Python Language List

Internal

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Overview

A list is a mutable sequence type that contains zero or more elements and whose elements can be of different types. The elements of a list are ordered. As mentioned, the list is mutable, in that a list can be changed in-place, new elements can be added to it, and existing elements can be overwritten. Unlike a set, a list can contain the same element multiple times.

List type()

The function type() applied to a list returns: <class 'list'>

To check whether an instance is a list:

i = ...
if type(i) is list:
  ...

For list subclasses:

i = ...
if isinstance(i, list):
  ...

Access a List

Size of a List

The number of elements is given by the len() function:

l = [...]
print(len(l))

Iterate over a List

l = ['A', 'B', 'C']
for i, e in enumerate(l):
    print(f'index: {i}, element: {e}')

Slices

Assign the sublist to l:

l = l[:-1]

Modify a List

Modify Individual Elements

Append an Element

l.append(e)

Delete the Last Element

del l[-1]

List Processing

TO DEPLETE

Join the List Elements in a String

Join the elements of the given list in a string, using '-' as separator:

li = ['a', 'b']
s = '-'.join(li)

Only works if the list elements are strings.

Extract Elements from the Tail of the List Starting with a Certain Index

l = [1, 2, 3]
print(l[0:]) # prints [1, 2, 3]
print(l[1:]) # prints [2, 3]
print(l[2:]) # prints [3]
print(l[3:]) # prints [] (empty list)
print(l[4:]) # prints [] (empty list)

Extract Elements from the Head of the List Counting from the Tail

TODO