Python - List Methods

Question 1

Return - none
Args - ( some number / string / list / etc )
___________
adds a single item to the existing list. It doesn’t return a new list; rather it modifies the original list.

Answer 1

list.append(item)

Question 2

Return - none
Args - ( some list to add to end )
___________
extends the list by adding all items of a list (passed as an argument) to the end.

Answer 2

list1.extend(list2)

Question 3

Return - none
Args - ( index, value to insert )
___________
inserts an element to the list at a given index.

Answer 3

list.insert(index, element)

Question 4

Return - none
Args - ( value to insert )
___________
searches for the given element in the list and removes the first matching element.

Answer 4

list.remove(element)

Question 5

Return - none
Args - ( value to find )
___________
finds the given element in a list and returns its position.

However, if the same element is present more than once, index() method returns its smallest/first position.

If not found, it raises a ValueError exception indicating the element is not in the list.

Answer 5

list.index(element)

Question 6

Return - none
Args - ( value to count )
___________
counts how many times an element has occurred in a list and returns it.

Answer 6

list.count(element)

Question 7

Return - none
Args - ( optional index to remove from the list )
___________
takes a single argument (index) and removes the item present at that index.

If the index passed to the pop() method is not in range, it throws IndexError: pop index out of range exception.

The parameter passed to the pop() method is optional. If no parameter is passed, the default index -1 is passed as an argument which returns the last item.

Answer 7

list.pop(index)

Question 8

Return - none
Args - none
___________
reverses the elements of a given list.

Answer 8

list.reverse()

Question 9

Return - none
Args - ( optional function that acts as key for the sort comparison, reverse = True/False )
___________
sorts the elements of a given list in a specific order - Ascending or Descending.

Answer 9

list.sort( key= … , reverse= … )

Question 10

Return - the new sorted list
Args - ( list, optional function that acts as key for the sort comparison, reverse = True/False )
___________
sorts the elements of a given list in a specific order - Ascending or Descending.

Answer 10

sorted( list, key= … , reverse= … )

Question 11

Return - returns an entirely new list (not a reference!)
Args - none
___________
if you need the original list unchanged when the new list is modified, you can use copy() method. This is called shallow copy.

Answer 11

new_list = list.copy()

~ same as ~

new_list = list[ : ]

~ same as ~

new_list = list( old_list )

Question 12

Return - none
Args - none
___________
removes all items from the list.

Answer 12

list.clear()

Question 13

Return - boolean
Args - ( iterable )
___________
returns:
True if at least one element of an iterable is true
False if all elements are false or if an iterable is empty

Answer 13

any(iterable)

Question 14

Return - boolean
Args - ( iterable )
___________
returns:
True - If all elements in an iterable are true
False - If any element in an iterable is false

Answer 14

all( iterable )

Question 15

Return - string
Args - ( object like a string, list, etc )
___________
returns a string containing printable representation of an object.

Answer 15

ascii( object )

Question 16

Return - a counter and an interable
Args - ( sequence/iterable, optional start index )
___________
adds counter to an iterable and returns it (the enumerate object.

The returned object is a enumerate object.

You can convert enumerate objects to list and tuple using list() and tuple() method respectively.

Answer 16

enumerate( iterable, start=0 )

Question 17

Return - a new iterable that passes the function
Args - ( function, iterable )
___________
filters the given iterable with the help of a function that tests each element in the iterable to be true or not.

Answer 17

filter( function, iterable )

Question 18

Return - iterator
Args - ( sets / tuples to turn into iterator, optional value that is the end of the sequence )
___________
creates an object which can be iterated one element at a time.

These objects are useful when coupled with loops like for loop, while loop.

Answer 18

iter( object, sentinel )

Question 19

Return - list
Args - ( opttional set / tuple / list / dict / etc )
___________
constructor creates a list in Python.

The list() constructor returns a mutable sequence list of elements.

If no parameters are passed, it creates an empty list
If iterable is passed as parameter, it creates a list of elements in the iterable

Answer 19

new_list = list( some optional iterable )

~ same as ~

new_list = [ ]

~ same as ~

new_list = list.copy( old list )

Question 20

Return - length of sequence
Args - ( opttional set / tuple / list / dict / etc )
___________
returns the number of items (length) in an object.

Answer 20

len( some sequence )

Question 21

Return - largest element in iterable or largest of 2+ parameters
Args - ( optional set / tuple / list / dict / etc )
or ( arg1, arg2, etc )
___________
returns the largest element in an iterable or largest of two or more parameters.

Answer 21

max( )

Question 22

Return - smallest element in iterable or smallest of 2+ parameters
Args - ( optional set / tuple / list / dict / etc )
or ( arg1, arg2, etc )
___________
returns the smallest element in an iterable or largest of two or more parameters.

Answer 22

min( )

Question 23

Return - list of mapped results
Args - ( mapping function, iterable to be mapped )
___________
applies a given function to each item of an iterable (list, tuple etc.) and returns a list of the results.

Answer 23

map( function, iterable, … )

Question 24

Return - reversed list
Args - ( some sequence )
___________
returns the reversed iterator of the given sequence.

*if you don’t want anything returned, just do list.reverse()

Answer 24

reversed( sequence )

Question 25

Return - sum
Args - ( iterable, optional value to start adding from )
___________
adds the items of an iterable and returns the sum.

Answer 25

sum( iterable, start )

Question 26

Return - iterator of tuples
Args - ( iterator1, iterator2, etc )
___________
take iterables (can be zero or more), makes iterator that aggregates elements based on the iterables passed, and returns an iterator of tuples.

Answer 26

zipped_object = zip( iterable1, iterable2, etc )

~ or ~

first_values, second_values, etc = zip( iterable1, iterable2, etc )