Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Coding > Python Interview > Flashcards

Python Interview Flashcards

1
Q

*args vs **kwargs

A

*args

  • when we don’t know how many arguments are going to be passed to a function
  • or if we want to pass a stored list or tuple of arguments to a function.

**kwargs

  • when we don’t know how many keyword arguments will be passed to a function, or it can be used to pass the values of a dictionary as keyword arguments.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

How do you make 3D plots/visualizations using NumPy/SciPy?

A

Like 2D plotting, 3D graphics is beyond the scope of NumPy and SciPy, but just as in the 2D case, packages exist that integrate with NumPy. Matplotlib provides basic 3D plotting in the mplot3d subpackage, whereas Mayavi provides a wide range of high-quality 3D visualization features, utilizing the powerful VTK engine.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Abstraction

A

Data Abstraction is providing only the required details and hiding the implementation from the world. It can be achieved in Python by using interfaces and abstract classes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Access specifiers

A

Python does not deprive access to an instance variable or function.

Python lays down the concept of prefixing the name of the variable, function or method with a single or double underscore to imitate the behavior of protected and private access specifiers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

add values to array

A

append(), extend() and the insert (i,x) functions.

Example:

a=arr.array(‘d’, [1.1 , 2.1 ,3.1] )

a.append(3.4)

print(a)

a.extend([4.5,6.3,6.8])

print(a)

a.insert(2,3.8)

print(a)

Output:

array(‘d’, [1.1, 2.1, 3.1, 3.4])

array(‘d’, [1.1, 2.1, 3.1, 3.4, 4.5, 6.3, 6.8])

array(‘d’, [1.1, 2.1, 3.8, 3.1, 3.4, 4.5, 6.3, 6.8])

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

remove values from array

A

pop() or remove() method. The difference between these two functions is that the former returns the deleted value whereas the latter does not.

Example:

a=arr.array(‘d’, [1.1, 2.2, 3.8, 3.1, 3.7, 1.2, 4.6])

print(a.pop())

print(a.pop(3))

a.remove(1.1)

print(a)

Output:

  1. 6
  2. 1

array(‘d’, [2.2, 3.8, 3.7, 1.2])

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Arrays vs Lists

A

Arrays and lists, in Python, have the same way of storing data.

But, arrays can hold only a single data type elements whereas lists can hold any data type elements.

ALso an array runs faster than a list because it alocates a block of memory.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Break, Continue and Pass

A

Break

  • Allows loop termination when some condition is met and the control is transferred to the next statement.

Continue

  • Allows skipping some part of a loop when some specific condition is met and the control is transferred to the beginning of the loop

Pass

  • Used when you need some block of code syntactically, but you want to skip its execution. This is basically a null operation. Nothing happens when this is executed.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Built-in types

A
  • Integers
  • Floating-point
  • Complex numbers
  • Strings
  • Boolean
  • Built-in functions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Capitalize the 1st letter of string

A
  • capitalize() method capitalizes the first letter of a string (and lowercase() lowers it)
  • If the string already consists of a capital letter at the beginning, then, it returns the original string.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Case sensitive

A

Python is a case sensitive language.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

create an empty class

A

An empty class is a class that does not have any code defined within its block. It can be created using the pass keyword. However, you can create objects of this class outside the class itself. IN PYTHON THE PASS command does nothing when its executed. it’s a null statement.

For example-

class a:

pass

obj=a()

obj.name=”xyz”

print(“Name = “,obj.name)

Output:

Name = xyz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Classes

A

Class in Python is created using the class keyword.

Example:

class Employee:

def __init__(self, name):

self.name = name

E1=Employee(“abc”)

print(E1.name)

Output:

abc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Comments

A

Comments in Python start with a # character. However, alternatively at times, commenting is done using docstrings(strings enclosed within triple quotes).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Comment multiple lines

A

Multi-line comments appear in more than one line.

  • All the lines to be commented are to be prefixed by a #.
  • block of string can be use for multi-lines comments, also called docstrings:
    • ”"”block
      of
      comment”””
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Compilation and Linking

A

Compiling and linking allows the new extensions to be compiled properly without any error and the linking can be done only when it passes the compiled procedure.

If the dynamic loading is used then it depends on the style that is being provided with the system. The python interpreter can be used to provide the dynamic loading of the configuration setup files and will rebuild the interpreter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Type Conversion (casting)

A

Type conversion refers to the conversion of one data type iinto another (casting).

  • int() – converts any data type into integer type
  • float() – converts any data type into float type
  • ord() – converts characters into integer
  • hex() – converts integers to hexadecimal
  • oct() – converts integer to octal
  • tuple() – This function is used to convert to a tuple.
  • set() – This function returns the type after converting to set.
  • list() – This function is used to convert any data type to a list type.
  • dict() – This function is used to convert a tuple of order (key,value) into a dictionary.
  • str() – Used to convert integer into a string.
  • complex(real,imag) – This functionconverts real numbers to complex(real,imag) number.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Deep vs Shallow copy

A

Shallow copy is used when a new instance type gets created and it keeps the values that are copied in the new instance. Shallow copy is used to copy the reference pointers just like it copies the values. These references point to the original objects and the changes made in any member of the class will also affect the original copy of it. Shallow copy allows faster execution of the program and it depends on the size of the data that is used.

Deep copy is used to store the values that are already copied. Deep copy doesn’t copy the reference pointers to the objects. It makes the reference to an object and the new object that is pointed by some other object gets stored. The changes made in the original copy won’t affect any other copy that uses the object. Deep copy makes execution of the program slower due to making certain copies for each object that is been called.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Delete files

A

import os

os.remove(“xyz.txt”)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Dictionary

A
  • built-in datatype. It defines one-to-one relationship between
  • keys and values pair
  • it is indexed by keys
  • mutable
  • iterable
  • curly brackets
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Django vs Flask

A

Django and Flask map the URL’s or addresses typed in the web browsers to functions in Python.

Flask is much simpler compared to Django but, Flask does not do a lot for you meaning you will need to specify the details, whereas Django does a lot for you wherein you would not need to do much work.

Django consists of prewritten code, which the user will need to analyze whereas Flask gives the users to create their own code, therefore, making it simpler to understand the code. Technically both are equally good and both contain their own pros and cons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Django, Pyramid and Flask.

A
  • Flask is a “microframework” primarily build for a small application with simpler requirements. In flask, you have to use external libraries. Flask is ready to use.
  • Pyramid is built for larger applications. It provides flexibility and lets the developer use the right tools for their project. The developer can choose the database, URL structure, templating style and more. Pyramid is heavy configurable.
  • Django can also be used for larger applications just like Pyramid. It includes an ORM (object-relational-mapping) - like database object in the code.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Django architecture

A

Django MVT Pattern:

The developer provides the Model, the view and the template then just maps it to a URL and Django does the magic to serve it to the user.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Inheritance styles in Django

A

In Django, there are three possible inheritance styles:

  • Abstract Base Classes: This style is used when you only want parent’s class to hold information that you don’t want to type out for each child model.
  • Multi-table Inheritance: This style is used If you are sub-classing an existing model and need each model to have its own database table.
  • Proxy models: You can use this model, If you only want to modify the Python level behavior of the model, without changing the model’s fields.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Session in Django

A
  • Django provides a session that lets you store and retrieve data on a per-site-visitor basis.
  • Django abstracts the process of sending and receiving cookies, by placing a session ID cookie on the client side, and storing all the related data on the server side.
  • The data itself is not stored client side. This is nice from a security perspective.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Django templates

A
  • The template is a simple text file.
  • It can create any text-based format like XML, CSV, HTML, etc.
  • A template contains variables that get replaced with values when the template is evaluated and tags (% tag %) that control the logic of the template.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

VIEW in Django

A

from django.http import HttpResponse

import datetime

def Current_datetime(request):

now = datetime.datetime.now()

html = “It is now %s % now

return HttpResponse(html)

Returns the current date and time, as an HTML document

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Docstrings

A
  • Docstrings are not actually comments, but, they are documentation strings.
  • These docstrings are within triple quotes.
  • They are not assigned to any variable and therefore, at times, serve the purpose of comments as well.
  • ””” Using docstring as a comment.
    This code divides 2 numbers “””
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Encapsulation

A

Encapsulation means binding the code and the data together. A Python class is an example of encapsulation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Flask

A

Flask is a web microframework for Python based on “Werkzeug, Jinja2 and good intentions” BSD license. Werkzeug and Jinja2 are two of its dependencies.

  • This means it will have little to no dependencies on external libraries.
  • It makes the framework light while there is a little dependency to update and fewer security bugs.
  • A session basically allows you to remember information from one request to another. In a flask, a session uses a signed cookie so the user can look at the session contents and modify.
  • The user can modify the session if only it has the secret key Flask.secret_key.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Functions

A
  • A function is a block of code which is executed only when it is called.
  • To define a Python function, the def keyword is used.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Generators

A

Functions that return an iterable set of items are called generators.

example: function that returns a list

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Get Google cache age of any URL or web page

A

http://webcache.googleusercontent.com/search?q=cache:URLGOESHERE

Example:

http://webcache.googleusercontent.com/search?q=cache:billygustave.com

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

help() vs dir()

A
  • help() and dir() both functions are accessible from the Python interpreter and used for viewing a consolidated dump of built-in functions.

help()

  • returns/displays the docstring for a function/class/module
  • help([object])

dir()

  • list all functions and variable names in a module
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

import modules

A

Modules can be imported using the import keyword. You can import modules in three ways- Example: 1 2 3

import array #importing using the original module name

import array as arr # importing using an alias name

from array import * #imports everything present in the array module

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Indentation

A
  • Indentation is necessary for Python. It specifies a block of code.
  • All code within loops, classes, functions, etc is specified within an indented block. It is usually done using four space characters.
  • If your code is not indented necessarily, it will not execute accurately and will throw errors as well.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

negative indexes

A

The negative index is used to remove any new-line spaces from the string and allow the string to except the last character that is given as S[:-1]. The negative index is also used to show the index to represent the string in correct order.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Inheritance

A

Inheritance allows One class to gain all the members(say attributes and methods) of another class. Inheritance provides code reusability, makes it easier to create and maintain an application. The class from which we are inheriting is called super-class and the class that is inherited is called a derived / child class.

They are different types of inheritance supported by Python:

  1. Single Inheritance – where a derived class acquires the members of a single super class.
  2. Multi-level inheritance – a derived class d1 in inherited from base class base1, and d2 are inherited from base2.
  3. Hierarchical inheritance – from one base class you can inherit any number of child classes
  4. Multiple inheritance – a derived class is inherited from more than one base class.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Iterators

A

objects which can be traversed though or iterated upon.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Lambda

A
  • An anonymous function is known as a lambda function.
  • This function can have any number of parameters but, can have just one statement.
40
Q

len()

A
  • returns count or length or how many elements in an object

It is used to determine the length of a string, a list, an array, etc. Example: 1 2 stg=’ABCD’ len(stg)

41
Q

Libraries

A

Python libraries are a collection of Python packages.

Some of the majorly used python libraries are – Numpy, Pandas, Matplotlib, Scikit-learn and many more.

42
Q

LIST vs TUPLES

A

LIST

  • Lists are mutable i.e they can be edited.
  • Lists are slower than tuples.
  • Syntax: list_1 = [10, ‘Chelsea’, 20]

TUPLES

  • Tuples are immutable (tuples are lists which can’t be edited).
  • Tuples are faster than list.
  • Syntax: tup_1 = (10, ‘Chelsea’ , 20)
43
Q

Lowercase

A

To convert a string to lowercase, lower() function can be used.

“string”.lower()

44
Q

map()

A

map function executes the function given as the first argument on all the elements of the iterable given as the second argument. If the function given takes in more than 1 arguments, then many iterables are given.

45
Q

Why isn’t all the memory de-allocated upon exit?

A
  • Whenever Python exits, especially those Python modules which are having circular references to other objects or the objects that are referenced from the global namespaces are not always de-allocated or freed.
  • It is impossible to de-allocate those portions of memory that are reserved by the C library.
  • On exit, because of having its own efficient clean up mechanism, Python would try to de-allocate/destroy every other object.
46
Q

Modules

A
  • Python modules are files containing Python code. This code can either be functions classes or variables.
  • A Python module is a .py file containing executable code.
  • Some of the commonly used built-in modules are:
    • os
    • sys
    • math
    • random
    • datatime
    • JSON
47
Q

monkey patching

A

In Python, the term monkey patch only refers to dynamic modifications of a class or module at run-time.

Consider the below example:

m.py

class MyClass:

def f(self):

print “f()”

We can then run the monkey-patch testing like this: .

import m

def monkey_f(self):

print “monkey_f()”

m.MyClass.f = monkey_f

obj = m.MyClass()

obj.f()

The output will be as below:

monkey_f()

As we can see, we did make some changes in the behavior of f() in MyClass using the function we defined, monkey_f(), outside of the module m.

48
Q

Which of the following statements create a dictionary?

A

a) d = {}
b) d = {“john”:40, “peter”:45}
c) d = {40:”john”, 45:”peter”}
d) d = (40:”john”, 45:”50”)

Answer:

a, b & c. Dictionaries are created by specifying keys and values.

49
Q

When will the else part of try-except-else be executed?

A

a) always
b) when an exception occurs
c) when no exception occurs
d) when an exception occurs into except block

Answer:

c) when no exception occurs

The else part is executed when no exception occurs.

50
Q

Which one of these is floor division?

A

a) /
b) //
c) %
d) None of the mentioned

Answer:

b) //

51
Q

What is the maximum possible length of an identifier?

A

a) 31 characters
b) 63 characters
c) 79 characters
d) None of the above

Answer:

d) None of the above

Identifiers can be of any length.

52
Q

Which of the following is an invalid statement?

A

a) abc = 1,000,000
b) a b c = 1000 2000 3000
c) a,b,c = 1000, 2000, 3000
d) a_b_c = 1,000,000

Answer:

b) a b c = 1000 2000 3000

Spaces are not allowed in variable names.

53
Q

Why are local variable names beginning with an underscore discouraged?

A

a) they are used to indicate a private variables of a class
b) they confuse the interpreter
c) they are used to indicate global variables
d) they slow down execution

Answer:

a) they are used to indicate a private variable of a class

As Python has no concept of private variables, leading underscores are used to indicate variables that must not be accessed from outside the class.

54
Q

To open a file c:scores.txt for writing, we use

A

a) outfile = open(“c:scores.txt”, “r”)
b) outfile = open(“c:scores.txt”, “w”)
c) outfile = open(file = “c:scores.txt”, “r”)
d) outfile = open(file = “c:scores.txt”, “o”)

Answer: b)

The location contains double slashes ( ) and w is used to indicate that file is being written to.

55
Q

Suppose list1 is [2, 33, 222, 14, 25], What is list1[-1] ?

A

a) Error
b) None
c) 25
d) 2

Answer:

c) 25

The index -1 corresponds to the last index in the list.

56
Q

What is the output of the following?

A

try:

if ‘1’ != 1:

raise “someError”

else:

print(“someError has not occured”)

except “someError”:

print (“someError has occured”)

a) someError has occured
b) someError has not occured
c) invalid code
d) none of the above

Answer:

c) invalid code

A new exception class must inherit from a BaseException. There is no such inheritance here.

57
Q

What is the output of the following?

A

f = None

for i in range (5):

with open(“data.txt”, “w”) as f:

if i > 2:

break

print f.closed

a) True
b) False
c) None
d) Error

Answer: a) True

The WITH statement when used with open file guarantees that the file object is closed when the with block exits.

58
Q

Multiple Inheritance

A

Multiple inheritance means that a class can be derived from more than one parent classes. Python does support multiple inheritance, unlike Java.

59
Q

Multithreading

A
  1. Python has a multi-threading package but if you want to multi-thread to speed your code up, then it’s usually not a good idea to use it.
  2. Python has a construct called the Global Interpreter Lock (GIL). The GIL makes sure that only one of your ‘threads’ can execute at any one time. A thread acquires the GIL, does a little work, then passes the GIL onto the next thread.
  3. This happens very quickly so to the human eye it may seem like your threads are executing in parallel, but they are really just taking turns using the same CPU core.
  4. All this GIL passing adds overhead to execution. This means that if you want to make your code run faster then using the threading package often isn’t a good idea.
60
Q

Namespace

A
  • A namespace is a naming system used to make sure that names are unique to avoid naming conflicts.
61
Q

How to get indices of N maximum values in a NumPy array?

A

We can get the indices of N maximum values in a NumPy array using the below code:

import numpy as np

arr = np.array([1, 3, 2, 4, 5])

print(arr.argsort()[-3:][::-1])

Output

[4 3 1]

62
Q

NumPy arrays vs lists

A
  1. Python’s lists are efficient general-purpose containers. They support (fairly) efficient insertion, deletion, appending, and concatenation, and Python’s list comprehensions make them easy to construct and manipulate.
  2. They have certain limitations: they don’t support “vectorized” operations like elementwise addition and multiplication, and the fact that they can contain objects of differing types mean that Python must store type information for every element, and must execute type dispatching code when operating on each element.
  3. NumPy is not just more efficient; it is also more convenient. You get a lot of vector and matrix operations for free, which sometimes allow one to avoid unnecessary work. And they are also efficiently implemented.
  4. NumPy array is faster and You get a lot built in with NumPy, FFTs, convolutions, fast searching, basic statistics, linear algebra, histograms, etc.
63
Q

What is the difference between NumPy and SciPy?

A
  1. In an ideal world, NumPy would contain nothing but the array data type and the most basic operations: indexing, sorting, reshaping, basic elementwise functions, etc.
  2. All numerical code would reside in SciPy. However, one of NumPy’s important goals is compatibility, so NumPy tries to retain all features supported by either of its predecessors.
  3. Thus NumPy contains some linear algebra functions, even though these more properly belong in SciPy. In any case, SciPy contains more fully-featured versions of the linear algebra modules, as well as many other numerical algorithms.
  4. If you are doing scientific computing with python, you should probably install both NumPy and SciPy. Most new features belong in SciPy rather than NumPy.
64
Q

Is Numpy better than lists?

A

We use python numpy array instead of a list because of the below three reasons:

  • Less Memory
  • Fast
  • Convenient
65
Q

How do you calculate percentiles with Python/ NumPy?

A

We can calculate percentiles with the following code

import numpy as np

a = np.array([1,2,3,4,5])

p = np.percentile(a, 50) #Returns 50th percentile, e.g. median

print(p)

Output

3

66
Q

object()

A
  • It returns a featureless object that is a base for all classes.
  • Also, it does not take any parameters.
67
Q

OOps concepts

A

Python is an object-oriented programming language. This means that any program can be solved in python by creating an object model. However, Python can be treated as procedural as well as structural language.

68
Q

IS,IN, NOT operators

A

IS/IS NOT

  • Identity operator
  • IS - compares 2 object and see if the are the same
    • returns true is they are the same: if x is y:
  • IS NOT - compares 2 objects and see if they are different
    • returns true is they are not same: if x is not y:

IN/NOT IN

  • Membership operator
  • IN - check to see if object is in a sequence
    • returns true is it is: if x in y:
  • NOT IN - check to see if object is not in a sequence
    • returns true is it is not: if x not in y:

NOT

  • returns reverse/opposite of any conditional statement
69
Q

Ternary operators

A
  • [on_true] if [expression] else [on_false]
  • it’s a represention of:
    if [expression]:
    [on_true]
    else
    [on_false]
70
Q

Packages

A
  • namespaces containing multiple modules
71
Q

PEP

A

PEP stands for Python Enhancement Proposal. It is a set of rules that specify how to format Python code for maximum readability.

72
Q

Pickling vs Unpickling

A
  • import pickle

Pickling

  • Pickle module accepts any Python object and converts it into a string representation and dumps it into a file by using dump function.
  • the python object is converted into a byte stream
  • serialization
  • pickled_string = pickle.dumps(python_object)

Unpickling

  • Process of retrieving original Python objects from the stored string representation.
  • the byte stream is converted back into a python object
  • de-serialization
  • python_object = pickle.loads(pickled_string)
73
Q

Polymorphism

A

Polymorphism means the ability to take multiple forms. So, for instance, if the parent class has a method named ABC then the child class also can have a method with the same name ABC having its own parameters and variables. Python allows polymorphism.

74
Q

Write a program in Python to execute the Bubble sort algorithm.

A

def bs(a): # a = name of list
b=len(a)-1 # minus 1 because we always compare 2 adjacent values

for x in range(b):
for y in range(b-x):
if a[y]>a[y+1]:
a[y],a[y+1]=a[y+1],a[y]
return a
a=[32,5,3,6,7,54,87]
bs(a)

Output: [3, 5, 6, 7, 32, 54, 87]

75
Q

Write a program in Python to check if a number is prime.

A

a=int(input(“enter number”))
if a>1:
for x in range(2,a):
if(a%x)==0:
print(“not prime”)
break
else:
print(“Prime”)
else:
print(“not prime”)

Output:
enter number 3

Prime

76
Q

Write a program in Python to check if a sequence is a Palindrome.

A

a=input(“enter sequence”)
b=a[::-1]
if a==b:
print(“palindrome”)
else:
print(“Not a Palindrome”)

Output:
enter sequence 323

palindrome

77
Q

Write a program to produce Fibonacci series in Python.

A

Enter number of terms needed #0,1,1,2,3,5….
a=int(input(“Enter the terms”))
f=0 #first element of series
s=1 #second element of series
if a<=0:
print(“The requested series is “,f)
else:
print(f,s,end=” “)
for x in range(2,a):
next=f+s
print(next,end=” “)
f=s
s=next

Output:
Enter the terms 5 0 1 1 2 3

78
Q

Write a sorting algorithm for a numerical dataset in Python.

A

The following code can be used to sort a list in Python:
list = [“1”, “4”, “0”, “6”, “9”]
list = [int(i) for i in list]
list.sort()
print (list)

79
Q

Write a one-liner that will count the number of capital letters in a file. Your code should work even if the file is too big to fit in memory.

A

Let us first write a multiple line solution and then convert it to one-liner code.
with open(SOME_LARGE_FILE) as fh:
count = 0
text = fh.read()
for character in text:
if character.isupper():
count += 1

We will now try to transform this into a single line.
count sum(1 for line in fh for character in line if character.isupper())
80
Q

Write a program in Python to produce Star triangle.

A 
def pyfunc(r):
 for x in range(r):
 print(' '\*(r-x-1)+'\*'\*(2\*x+1)) pyfunc(9)

Output:

*
***
*****
*******
*********
***********
*************
***************
*****************

81
Q

Web Scrapping example

A

from bs4 import BeautifulSoup

import requests

import sys

url = ‘http://www.imdb.com/chart/top’

response = requests.get(url)

soup = BeautifulSoup(response.text)

tr = soup.findChildren(“tr”)

tr = iter(tr)

next(tr)

for movie in tr:

title = movie.find(‘td’, {‘class’: ‘titleColumn’} ).find(‘a’).contents[0]

year = movie.find(‘td’, {‘class’: ‘titleColumn’} ).find(‘span’, {‘class’: ‘secondaryInfo’}).contents[0]

rating = movie.find(‘td’, {‘class’: ‘ratingColumn imdbRating’} ).find(‘strong’).contents[0]

row = title + ‘ - ‘ + year + ‘ ‘ + ‘ ‘ + rating

print(row)

82
Q

Looking at the below code, write down the final values of A0, A1, …An.

A 
A0 = dict(zip(('a','b','c','d','e'),(1,2,3,4,5)))
A1 = range(10)
A2 = sorted([i for i in A1 if i in A0])
A3 = sorted([A0[s] for s in A0])
A4 = [i for i in A1 if i in A3]
A5 = {i:i\*i for i in A1}
A6 = [[i,i\*i] for i in A1] print(A0,A1,A2,A3,A4,A5,A6)

Ans: The following will be the final outputs of A0, A1, … A6
A0 = {‘a’: 1, ‘c’: 3, ‘b’: 2, ‘e’: 5, ‘d’: 4} # the order may vary
A1 = range(0, 10)
A2 = []
A3 = [1, 2, 3, 4, 5]
A4 = [1, 2, 3, 4, 5]
A5 = {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}
A6 = [[0, 0], [1, 1], [2, 4], [3, 9], [4, 16], [5, 25], [6, 36], [7, 49], [8, 64], [9,

83
Q

PYTHON features

A
  • Python is an interpreted language. That means that, unlike languages like C and its variants, Python does not need to be compiled before it is run. Other interpreted languages include PHP and Ruby.
  • Python is dynamically typed, this means that you don’t need to state the types of variables when you declare them or anything like that. You can do things like x=111 and then x=”I’m a string” without error
  • Python is well suited to object orientated programming in that it allows the definition of classes along with composition and inheritance. Python does not have access specifiers (like C++’s public, private).
  • In Python, functions are first-class objects. This means that they can be assigned to variables, returned from other functions and passed into functions. Classes are also first class objects
  • Writing Python code is quick but running it is often slower than compiled languages. Fortunately，Python allows the inclusion of C based extensions so bottlenecks can be optimized away and often are. The numpy package is a good example of this, it’s really quite quick because a lot of the number crunching it does isn’t actually done by Python
  • Python finds use in many spheres – web applications, automation, scientific modeling, big data applications and many more. It’s also often used as “glue” code to get other languages and components to play nice.
84
Q

Global vs Local variables

A

Global Variables:

  • Variables declared outside a function or in global space are called global variables. These variables can be accessed by any function in the program.
  • declare a global variable inside a function using keyword global

Local Variables:

  • Any variable declared inside a function is known as a local variable. This variable is present in the local space and not in the global space.
85
Q

Python an interpreted language

A

An interpreted language is any programming language which is not in machine level code before runtime.

86
Q

Memory Management in Python

A
  • Memory management in python is managed by Python private heap space. All Python objects and data structures are located in a private heap. The programmer does not have access to this private heap. The python interpreter takes care of this instead.
  • The allocation of heap space for Python objects is done by Python’s memory manager. The core API gives access to some tools for the programmer to code.
  • Python also has an inbuilt garbage collector, which recycles all the unused memory and so that it can be made available to the heap space.
87
Q

Is Python a Programming or Scripting language?

A

Python is capable of scripting, but in general sense, it is considered as a general-purpose programming language.

88
Q

Install Python on Windows with path variable

A

To install Python on Windows, follow the below steps:

  • Download python from this link: https://www.python.org/downloads/
  • After this, install it on your PC. Look for the location where PYTHON has been installed on your PC using the following command on your command prompt: cmd python.
  • Then go to advanced system settings and add a new variable and name it as PYTHON_NAME and paste the copied path.
  • Look for the path variable, select its value and select ‘edit’.
  • Add a semicolon towards the end of the value if it’s not present and then type %PYTHON_HOME%
89
Q

PYTHONPATH

A

It is an environment variable which is used when a module is imported. Whenever a module is imported, PYTHONPATH is also looked up to check for the presence of the imported modules in various directories. The interpreter uses it to determine which module to load.

90
Q

Generate Random numbers

A
  • Random module is the standard module that is used to generate a random number.
  • The method is defined as:
  • *import** random
    random. random
  • The statement random.random() method return the floating point number that is in the range of [0, 1). The function generates random float numbers. The methods that are used with the random class are the bound methods of the hidden instances.
  • The instances of the Random can be done to show the multi-threading programs that creates a different instance of individual threads. The other random generators that are used in this are:
  1. randrange(a, b): it chooses an integer and define the range in-between [a, b). It returns the elements by selecting it randomly from the range that is specified. It doesn’t build a range object.
  2. uniform(a, b): it chooses a floating point number that is defined in the range of [a,b).Iyt returns the floating point number
  3. normalvariate(mean, sdev): it is used for the normal distribution where the mu is a mean and the sdev is a sigma that is used for standard deviation.
  4. The Random class that is used and instantiated creates an independent multiple random number generators.
91
Q

randomize the items of a list in place

A

from random import shuffle

x = [‘Keep’, ‘The’, ‘Blue’, ‘Flag’, ‘Flying’, ‘High’]

shuffle(x)

92
Q

Range vs xRange

A

Both creates list or number to use/iterate through

Range

  • range returns list of object
  • generates a static list at run-time which takes memory space
  • not ideal for big range list or memory sensitive systems
  • can run the risk of Memory Error if run out of memory

xRange

  • xrange returns an xrange object
  • creates value when needed using yield technique which uses a generator object.
  • good for memory sensitive systems such as cellphone
  • ideal for big range list
93
Q

Save An Image Locally Using Python

A

import urllib.request

urllib.request.urlretrieve(“URL”, “local-filename.jpg”)

94
Q

self

A
  • Self is an instance or an object of a class.
  • In Python, this is explicitly included as the first parameter. However, this is not the case in Java where it’s optional.
  • It helps to differentiate between the methods and attributes of a class with local variables.
  • The self variable in the init method refers to the newly created object while in other methods, it refers to the object whose method was called.
95
Q

split()

A

split() method is used to separate a given string in Python.

Example:

a=“edureka python”

print(a.split())

Output:

[‘edureka’, ‘python’]

96
Q

split(), sub(), subn()

A

To modify the strings, Python’s “re” module is providing 3 methods. They are:

split() – uses a regex pattern to “split” a given string into a list.

sub() – finds all substrings where the regex pattern matches and then replace them with a different string

subn() – it is similar to sub() and also returns the new string along with the no. of replacements.

97
Q

[::-1]

A

[::-1] is used to reverse the order of an array or a sequence.

98
Q

__init__

A
  • __init__ is a method or constructor in Python.
  • This method is automatically called to allocate memory when a new object/ instance of a class is created.
  • All classes have the __init__ method.

Coding (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions