Intermediate Python Interview Questions

Question 1

Explain split(), sub(), subn() methods of “re” module in Python?

Answer 1

These methods belong to the Python RegEx or ‘re’ module and are used to modify strings.

split(): This method is used to split a given string into a list.

sub(): This method is used to find a substring where a regex pattern matches, and then it replaces the matched substring with a different string.

subn(): This method is similar to the sub() method, but it returns the new string, along with the number of replacements.

Question 2

What do you mean by Python literals?

Answer 2

Generally, literals are a notation for representing a fixed value in source code. They can also be defined as raw values or data given in variables or constants. Python has different types of literal such as:

1. String literals
2. Numeric literals
3. Boolean literals
4. Literal Collections
5. Special literals

Literals supported by python are listed below:

String Literals

These literals are formed by enclosing text in the single or double quotes.

For Example:

“Intellipaat”

‘45879’

Numeric Literals

Python numeric literals support three types of literals

Integer:I=10

Float: i=5.2

Complex:1.73j

Boolean Literals

Boolean literals help to denote boolean values. It contains either True or False.

x=True

Question 3

What is a map function in Python?

Answer 3

The map() function in Python has two parameters, function and iterable. The map() function takes a function as an argument and then applies that function to all the elements of an iterable, passed to it as another argument. It returns an object list of results.

For example:

def calculateSq(n):

return n*n

numbers = (2, 3, 4, 5)

result = map( calculateSq, numbers)

print(result)

Question 4

What are the generators in python?

Answer 4

Generator refers to the function that returns an iterable set of items.

Question 5

What are python iterators?

Answer 5

These are the certain objects that are easily traversed and iterated when needed.

Question 6

Do we need to declare variables with data types in Python?

Answer 6

No. Python is a dynamically typed language, I.E., Python Interpreter automatically identifies the data type of a variable based on the type of value assigned to the variable.

Question 7

What are Dict and List comprehensions?

Answer 7

Python comprehensions are like decorators, that help to build altered and filtered lists, dictionaries, or sets from a given list, dictionary, or set. Comprehension saves a lot of time and code that might be considerably more complex and time-consuming.

Comprehensions are beneficial in the following scenarios:

• Performing mathematical operations on the entire list
• Performing conditional filtering operations on the entire list
• Combining multiple lists into one
• Flattening a multi-dimensional list

For example:

my_list = [2, 3, 5, 7, 11]

squared_list = [x**2 for x in my_list] # list comprehension

output => [4 , 9 , 25 , 49 , 121]

squared_dict = {x:x**2 for x in my_list} # dict comprehension

output => {11: 121, 2: 4 , 3: 9 , 5: 25 , 7: 49}

Question 8

How do you write comments in python?

Answer 8

Comments in Python

Python Comments are the statement used by the programmer to increase the readability of the code. With the help of #, you can define the single comment and the other way to do commenting is to use the docstrings(strings enclosed within triple quotes).
For example:

print(“Comments in Python “)

Question 9

Is multiple inheritance supported in Python?

Answer 9

Yes, unlike Java, Python provides users with a wide range of support in terms of inheritance and its usage. Multiple inheritance refers to a scenario where a class is instantiated from more than one individual parent class. This provides a lot of functionality and advantages to users.

Question 10

What is the difference between range & xrange?

Answer 10

Functions in Python, range() and xrange() are used to iterate in a for loop for a fixed number of times. Functionality-wise, both these functions are the same. The difference comes when talking about Python version support for these functions and their return values.

RANGE() Method

• In Python 3, xrange() is not supported; instead, the range() function is used to iterate in for loops
• It returns a list
• It takes more memory as it keeps the entire list of iterating numbers in memory

XRANGE() Method

• The xrange() function is used in Python 2 to iterate in for loops
• It returns a generator object as it doesn’t really generate a static list at the run time
• It takes less memory as it keeps only one number at a time in memory

Question 11

What is pickling and unpickling?

Answer 11

The Pickle module accepts the Python object and converts it into a string representation and stores it into a file by using the dump function. This process is called pickling. On the other hand, the process of retrieving the original Python objects from the string representation is called unpickling.

Question 12

What do you understand by Tkinter?

Answer 12

Tkinter is a built-in Python module that is used to create GUI applications. It is Python’s standard toolkit for GUI development. Tkinter comes with Python, so there is no separate installation needed. You can start using it by importing it in your script.

Question 13

Is Python fully object oriented?

Answer 13

Python does follow an object-oriented programming paradigm and has all the basic OOPs concepts such as inheritance, polymorphism, and more, with the exception of access specifiers. Python doesn’t support strong encapsulation (adding a private keyword before data members). Although, it has a convention that can be used for data hiding, i.e., prefixing a data member with two underscores.

Question 14

Differentiate between NumPy and SciPy?

Answer 14

NumPY

• NumPy stands for Numerical Python
• It is used for efficient and general numeric computations on numerical data saved in arrays. E.g., sorting, indexing, reshaping, and more
• There are some linear algebraic functions available in this module, but they are not full-fledged

SciPy

• SciPy stands for Scientific Python
• This module is a collection of tools in Python used to perform operations such as integration, differentiation, and more
• Full-fledged algebraic functions are available in SciPy for algebraic computations

Question 15

Explain all file processing modes supported in Python?

Answer 15

Python has various file processing modes.

For opening files, there are three modes:

• read-only mode (r)
• write-only mode (w)
• read–write mode (rw)

For opening a text file using the above modes, we will have to append ‘t’ with them as follows:

• read-only mode (rt)
• write-only mode (wt)
• read–write mode (rwt)

Similarly, a binary file can be opened by appending ‘b’ with them as follows:

• read-only mode (rb)
• write-only mode (wb)
• read–write mode (rwb)

To append the content in the files, we can use the append mode (a):

• For text files, the mode would be ‘at’
• For binary files, it would be ‘ab’

Question 16

What do file-related modules in Python do? Can you name some file-related modules in Python?

Answer 16

Python comes with some file-related modules that have functions to manipulate text files and binary files in a file system. These modules can be used to create text or binary files, update their content, copy, delete, and more.

Some file-related modules are os, os.path, and shutil.os. The os.path module has functions to access the file system, while the shutil.os module can be used to copy or delete files.

Question 17

Explain the use of the ‘with’ statement and its syntax?

Answer 17

In Python, using the ‘with’ statement, we can open a file and close it as soon as the block of code, where ‘with’ is used, exits. In this way, we can opt for not using the close() method.

with open(“filename”, “mode”) as file_var:

Question 18

Write a code to display the contents of a file in reverse?

Answer 18

To display the contents of a file in reverse, the following code can be used:

for line in reversed(list(open(filename.txt))):

print(line.rstrip())

Question 19

Which of the following is an invalid statement?

1. xyz = 1,000,000
2. x y z = 1000 2000 3000
3. x,y,z = 1000, 2000, 3000
4. x_y_z = 1,000,000

Answer 19

Ans. 2 statement is invalid.

Question 20

Write a command to open the file c:\hello.txt for writing?

Answer 20

Command:

f= open(“hello.txt”, “wt”)

Question 21

What does len() do?

Answer 21

len() is an inbuilt function used to calculate the length of sequences like list, python string, and array.

my _list=[1,2,3,4,5]

len(my_list)

Question 22

What does *args and **kwargs mean?

Answer 22

• *args: It is used to pass multiple arguments in a function.
• **kwargs: It is used to pass multiple keyworded arguments in a function in python.

Question 23

How will you remove duplicate elements from a list?

Answer 23

To remove duplicate elements from the list we use the set() function.

Consider the below example:

demo_list=[5,4,4,6,8,12,12,1,5]

unique_list = list(set(demo_list))

output:[1,5,6,8,12]

Question 24

How can files be deleted in Python?

Answer 24

You need to import the OS Module and use os.remove() function for deleting a file in python.
consider the code below:

import os

os.remove(“file_name.txt”)

Question 25

How will you read a random line in a file?

Answer 25

We can read a random line in a file using the random module.

For example:

import random

def read_random(fname):

lines = open(fname).read().splitlines()

return random.choice(lines)

print(read_random (‘hello.txt’))

Question 26

Write a Python program to count the total number of lines in a text file?

Answer 26

Method 1:

with open(r”myfile.txt”, ‘r’) as fp:

lines = len(fp.readlines())

print(‘Total Number of lines:’, lines)

Method 2:

with open(r”myfile.txt”, ‘r’) as fp:

for count, line in enumerate(fp):

pass

print(‘Total Number of lines:’, count + 1)

Question 27

What would be the output if I run the following code block?

Answer 27

list1 = [2, 33, 222, 14, 25]

print(list1[-2])

14

33

25

Error

Ans. output:14

Question 28

What is the purpose of is, not and in operators?

Answer 28

Operators are referred to as special functions that take one or more values(operands) and produce a corresponding result.

• is: returns the true value when both the operands are true (Example: “x” is ‘x’)
• not: returns the inverse of the boolean value based upon the operands (example:”1” returns “0” and vice-versa.
• In: helps to check if the element is present in a given Sequence or not.

Question 29

Whenever Python exits, why isn’t all the memory de-allocated?

Answer 29

• 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 not possible 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 every object.

Question 30

How can the ternary operators be used in python?

Answer 30

The ternary operator is the operator that is used to show conditional statements in Python. This consists of the boolean true or false values with a statement that has to be checked.

Syntax:

[on_true] if [expression] else [on_false]x, y = 10, 20 count = x if x < y else y

Explanation:

The above expression is evaluated like if x

Question 31

How to add values to a python array?

Answer 31

In python, adding elements in an array can be easily done with the help of extend(),append() and insert() functions.
Consider the following example:

x=arr.array(‘d’, [11.1 , 2.1 ,3.1] )

x.append(10.1)

print(x) #[11.1,2.1,3.1,10.1]

x.extend([8.3,1.3,5.3])

print(x) #[11.1,2.1,3.1,10.1,8.3,1.3,5.3]

x.insert(2,6.2)

print(x) # [11.1,2.1,6.2,3.1,10.1,8.3,1.3,5.3]

Question 32

How to remove values to a python array?

Answer 32

Elements can be removed from the python array using pop() or remove() methods.

pop(): This function will return the removed element .

remove():It will not return the removed element.

Consider the below example :

x=arr.array(‘d’, [8.1, 2.4, 6.8, 1.1, 7.7, 1.2, 3.6])

print(x.pop())

print(x.pop(3))

x.remove(8.1)

print(x)

Output:

3. 6
4. 1 # element popped at 3 rd index

array(‘d’, [2.4, 6.8, 7.7, 1.2])

Question 33

Write a code to sort a numerical list in Python?

Answer 33

The following code can be used to sort a numerical list in Python:

list = [“2”, “5”, “7”, “8”, “1”]

list = [int(i) for i in list]

list.sort()

print (list)

Question 34

Can you write an efficient code to count the number of capital letters in a file?

Answer 34

The normal solution for this problem statement would be as follows:

with open(SOME_LARGE_FILE) as countletter:

count = 0
text = countletter.read()
for character in text:
if character.isupper():
count += 1

To make this code more efficient, the whole code block can be converted into a one-liner code using the feature called generator expression. With this, the equivalent code line of the above code block would be as follows:

count sum(1 for line in countletter for character in line if character.isupper())

Question 35

How will you reverse a list in Python?

Answer 35

The function list.reverse() reverses the objects of a list.

Question 36

How will you remove the last object from a list in Python?

Answer 36

list.pop(obj=list[-1]):

Here, −1 represents the last element of the list. Hence, the pop() function removes the last object (obj) from the list.

Question 37

How can you generate random numbers in Python?

Answer 37

This achieved with importing the random module,it is the module that is used to generate random numbers.

Syntax:

import random

random.random # returns the floating point random number between the range of [0,1].

Question 38

How will you convert a string to all lowercase?

Answer 38

lower() function is used to convert a string to lowercase.

For Example:

demo_string=’ROSES’

print(demo_string.lower())

Question 39

Why would you use NumPy arrays instead of lists in Python?

Answer 39

NumPy arrays provide users with three main advantages as shown below:

• NumPy arrays consume a lot less memory, thereby making the code more efficient.
• NumPy arrays execute faster and do not add heavy processing to the runtime.
• NumPy has a highly readable syntax, making it easy and convenient for programmers.

Question 40

What is Polymorphism in Python?

Answer 40

Polymorphism is the ability of the code to take multiple forms. Let’s say, if the parent class has a method named XYZ then the child class can also have a method with the same name XYZ having its own variables and parameters.

Question 41

Define encapsulation in Python?

Answer 41

encapsulation in Python refers to the process of wrapping up the variables and different functions into a single entity or capsule.Python class is the best example of encapsulation in python.

Question 42

What advantages do NumPy arrays offer over (nested) Python lists?

Answer 42

Nested Lists:

• Python lists are efficient general-purpose containers that support efficient operations like insertion,appending,deletion and concatenation.
• The limitations of lists are that they don’t support “vectorized” operations like element wise 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.

Numpy:

• NumPy is more efficient and more convenient as you get a lot of vector and matrix operations for free, which helps to avoid unnecessary work and complexity of the code.Numpy is also efficiently implemented when compared to nested
• NumPy array is faster and contains a lot of built-in functions which will help in FFTs, convolutions, fast searching, linear algebra,basic statistics, histograms,etc.