Mod 5 Flashcards
How are Modules identified? What do they consist of? How do you use them? How do they relate to the Python standard library?
- it is identified by its name
- forms the Python standard library (along with functions)
- consists of entities (functions, variables, constants, classes and objects)
- must import before using
Write the code to import the math module
import math
Where must the “import math” instruction be placed in the code?
It can go anywhere in the code, but must be placed before it is used.
Write the code to access the pi entity after the “import math” statement:
math.pi for example (math.pi/2)
Write the import statement to access the pi entity within the math module:
from math import pi
Write the code to access the pi entity after the “from math import pi” statement:
pi
for example pi/2
Write the code to import all entities from the math module:
from math import *
Write the code to import the math module with an alias of "m": Also, is the math module name usable? (for example math.pi)
import math as m
no
Write the code to import the pi entity with an alias of “PI”
from math import pi as PI
what does dir(module) do?
returns sorted list containing all entities names in the module
What does the random() function do? What is its syntax?
produces a random float number between 0 and 1.
random()
What does randrange() do? What is its syntax?
produces a random integer value within a specified range.
randrange(start, stop, step)
What does choice() do? What is its syntax?
Takes in a sequence (list for example) and chooses a random element
choice(sequence)
What does sample() do? What is its syntax?
draws the numbers randomly so they are unique and no duplicates sample(sequence, # to choose) sample of code: from random import * list=[1,2,3,4,5] print(sample(list,3))
What does the platform module do? What of the platform() function?
module - underlying platforms data (hardware, operating system, interpreter version info) function - environment description Sample of code: from platform import platform print(platform()) Linux-4.4.0-206-generic-x86_64-with
What does the machine() function do?
See generic name of the processor Sample of code: from platform import machine print(machine()) x86_64
What does the processor() function do?
See real processor name (if possible) Sample of code: from platform import processor print(processor()) #returns nothing for me
What does the system() function do?
See Operating System name Sample of code: from platform import system print(system()) Linux
What does the version() function do?
See Operating System version Sample of code: from platform import system print(version()) #238-Ubuntu SMP Tue Mar 16 07:52:37 UTC 2021
What does the python_implementation() function do?
see the python implementation Sample of code: from platform import python_implementation print(python_implementation()) CPython
What does python_version_tuple function do?
see 3 element function with the major part of Pythons version, the minor part, the patch level number Sample of code: from platform import python_version_tuple for atr in python_version_tuple(): print(atr) 3 7 10
How do functions, modules and packages relate to each other?
Packages contains modules and modules contain functions.
When a module is imported what happens to the module and its content?
- its content is implicitly executed by Python
- it initializes (which only happens once)
What happens to __name__ when its file is ran?
What happens when a file with __name__ is imported?
- when you run a file directly, its __name__ variable is set to __main__
- when a file is imported as a module, its __name__ variable is set to the files name (excluding .py)
Sample of code:
module.py file:
print(“I like python”) #output: I like python
print(__name__) output: __main__
main.py file:
import file #output: I like python
module
When underscores are added before and after a variable name what does it do?
It makes the variable personal/private. It is a convention however and users may or may not obey it.
True or False: Python is able to treat zip files as ordinary folders
True
What module is the path variable from? What does it do? Explain its behavior?
- Accessible through sys module
- It stores all locations that are searched to find a module (module requested by the import instruction)
- searches in order, based on the list
- the search starts with the first path’s element
Write the code to find a module, start the search in “‘C:\Users\user\py\modules” folder:
from sys import path
path.append('..\\modules')
import module
or
from sys import path
path.insert(1, 'C:\\Users\\user\\py\\modules')
import moduleHow do you transform a folder directory to a Python package?
Initialize by including the “__init__.py” file inside the package’s folder.
The content of the file is executed when any of the packages modules are imported. You can leave the file empty if you there are no special initializations.
Facts about the __init__.py file (4):
- The content of the file is executed when any of the packages modules are imported.
- You can leave the file empty if you there are no special initializations.
- the file can go anywhere in the package
- can have multiple init files per package
Where do you put the subtree to make it accessible to Python?
anywhere
Write the code to access the funS() function from the sigma module from the best, good, extra package(3):
from sys import path
path.append('..\\packages')
import extra.good.best.sigma
print(extra.good.best.sigma.funS())
or
from sys import path
path.insert(1, 'C:\\Users\\user\\py\\modules')
from extra.good.best.sigma import funS
print(funS())
or
from sys import path
path.append('..\\packages')
import extra.good.best.sigma as sig
print(sig.funS())What are the 2 steps that Python does when raising an exception?
- Stops the program
2. Creates data called an exception
What happens when an exception is handled? What of when it is not handled?
- the program will resume and execution can continue
- The program will be forcibly terminated and user will see an error message in the console
What is the output of the code when 1 and 1 are inputted?
firstNumber = int(input(“Enter the first number: “))
secondNumber = int(input(“Enter the second number: “))
try:
print(firstNumber / secondNumber)
except:
print(“This operation cannot be done.”)
print(“THE END.”)
1.0
THE END.
What is the output of the code when 1 and 0 are inputted?
firstNumber = int(input(“Enter the first number: “))
secondNumber = int(input(“Enter the second number: “))
try:
print(firstNumber / secondNumber)
except:
print(“This operation cannot be done.”)
print(“THE END.”)
This operation cannot be done.
THE END.
What is the output of:
try:
print("1")
x = 1 / 0
print("2")
except:
print("Oh dear, something went wrong...")
print(“3”)
1
Oh dear, something went wrong…
3
Facts about exceptions(8):
- except branches are searched in the same order as they appear in the code
- cannot duplicate exception names
- must have at least one except branch and cannot be used without try
- if any except branches are executed no other branches will be visited
- each exception raised falls into the first matching branch
- if none of the except branches matches the raised exception, the exception remains unhandled
- if an unnamed except branch exists, it must be the last
- put general exceptions towards the end
What is the name of the root exception?
BaseException
Is the below code legal?
def badFun(n):
try:
return 1 / n
except (ArithmeticError, BaseException):
print("Arithmetic Problem!")
return None
badFun(0)
print(“THE END.”)
Yes
True or False: If an exception is raised inside a function, it can be handled inside the function and outside the function.
True
What does raise do?
The keyword prompts Python to raise an exception to then handle the exception. This allows you to test your exception handling.
True or False: If raise is used in a function, it must be handled in an except branch only.
True
What does ASCII stand for? Facts (3)
American Standard Code for Information Interchange
- provides space for 256 different characters
- space for whitespaces
- Lower case are larger ints than Upper case
What is a code point?
Its a number which makes a character. For example A = 65
What does UTF stand for in UTF-8 and what it does.
- Derived from Unicode Transformation Format
- Uses as many bits for each of the code points as it really needs to represent them
String facts (6). How do they relate to whitespaces? Multilinestrings?
- Immutable sequences
- not able to modify the string using del, append, insert
- can use del to delete the whole string
- can create a new copy of a string to modify
- can index, iterate, slice
- can be concatenated and replicated
- whitespaces add to the length (space between words, new line \n)
- multiline strings can be delimited by triple quotes and triple apostrophes
What does the ord() function do?
Identifies a character’s ASCII/Unicode code point value
What does the chr() function do?
Takes a code point and returns its character
What is the output of:
alpha = “peplum”
print(alpha[1:3]) print(alpha[3:]) print(alpha[:3]) print(alpha[3:-2]) print(alpha[-3:4]) print(alpha[::2]) print(alpha[1::2])
ep lum pep l l ppu elm
What is the output of:
alphabet = “abcdefghijklmnopqrstuvwxyz”
print("f" not in alphabet)
print("F" not in alphabet)
print("1" not in alphabet)
print("ghi" not in alphabet)
print("Xyz" not in alphabet)
False True True False True
What do the min() and max() functions do? What if the argument is empty?
Finds the minimum and maximum element of the sequence. The argument cannot be empty or will return an exception.
What does the index() method do? What if the element is not in the sequence?
Searches the sequence from the beginning in order to find the first element of the value specified in its argument. If the element searched for is not in the sequence it return an exception.
What is the output of:
print(“aAbByYzZaA”.index(“b”))
print(“aAbByYzZaA”.index(“Z”))
print(“aAbByYzZaA”.index(“A”))
2
7
1
What does the list() function do?
It takes a string and creates a list containing all the strings characters.
What does the count() method do? What if the element isnt present?
It counts all occurrences of the element inside the sequence. Absence of the element doesn’t cause a exception.
What does the capitalize method do?
Creates a new string filled with characters taken from the source string.
If the first character inside the string is a letter, it will be converted to upper case. All remaining letters from the string will be converted to lower case.
What is the output of:
print(‘Captain Jack Sparrow”.capitalize())
Captain jack sparrow
Facts about applying methods to strings (3)
- the original string is not changed in any way
- the modified string is returned
- unless a variable is assigned to the modified string, it is gone and not saved
What does the center() method do?
It centers a string by adding spaces before and after the string.
What is the syntax of the center() method?
center(output length, delimiter)
What is the output of:
print(‘apple’.center(6,’*’))
apple*
What does the endswith() method do?
Checks if the given string ends with the specified argument and returns True or False
What does the find() method do?
It looks for a substring and returns the index of first occurrence of this substring. It doesnt generate an exception if the argument doesnt exist.
What is the output of:
t = 'theta'
print(t.find('eta'))
print(t.find('et'))
print(t.find('the'))
print(t.find('ha'))2
2
0
-1
What is the syntax of the find() method?
string.find(characters_to_find, start_index, stop_index)
What does the isalnum() method do?
Checks if the string contains only digits or alphabetical characters (letters) and returns True or False.
What does the isalpha() method do?
Checks if the string contains only letters. Returns True or False. Whitespaces are not letters.
What does the isdigit() method do?
Checks if the string contains only digits. Returns True or False.
What does the islower() method do?
Checks for lower case only. Returns True or False.
What does the isspace() method do?
Checks for whitespaces only. Returns True or False.
What does the isupper() method do?
Checks for upper case only. Returns True or False.
What does the join() method do?
Performs a join. The input is a list and outputs a string.
What is the output of:
a = [‘Curly’, ‘Larry’, ‘Moe’]
print(“,”.join(a))
Curly,Larry,Moe
What does the lower() method do?
Makes a copy of a source string, replaces all upper case letters with their lower case counterparts.
What does the lstrip() method do?
Returns a newly created string formed from the original one by removing all leading specified characters (letter, number, whitespaces).
What is the output of:
name = Mr. Magoo
print(name.lstrip(‘Mr.”)
Magoo (with space in front)
What does the replace() method do?
Returns a copy of the original string in which all occurrences of the first argument have been replaced by the second argument.
What is the syntax of the replace() method?
replace(first string, second string, number of replacements)
What does the rfind() method do?
Provides the index of where a string is. It starts the search from the right.
What is the syntax of the rfind() method?
rfind(string to find, starting search index, ending search index)
What does the rstrip() method do?
Returns a newly created string formed from the original one by removing the indicated elements (string, whitespaces, etc)
What does the split() method do?
Splits the string and builds a list of all detected substrings. It assumes the substrings are delimited by whitespaces.
What is the output of:
print(“phi chi\npsi”.split())
[‘phi’, ‘chi’, ‘psi’]
What does the startswith() method do?
It checks if a given string starts with the specified substring.
What does the strip method do?
Makes a new string lacking all the leading and trailing designated characters (whitespaces, letters, numbers).
What is the output of:
print(“Hello Harry!”.strip(‘H’))
ello Harry!
What does the swapcase() method do?
It swaps the case of all letters within the source string.
What does the title() method do?
Changes every word’s first letter to upper case during all others to lower case
What does the upper() method do?
Replaces all lower case letters to their upper case counterparts
Facts about comparing strings(4):
- It compares the code point values
- Compares the first different character in both strings
- if strings are identical at the beginning, the longer one is considered greater
- lower case letters are greater than their upper case counterparts
What is the output of: '10' == '010' '10' > '010' '10' > '8' '20' < '8' '20' < '80'
False True False True True
What is the difference between sorted() and sort()?
sorted() is a function that returns a new sorted list
sort() affects the list itself, no new list is created
What is the output of:
print(float(“1, 2”))
ValueError
