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Lists
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Last update: 03-12-2021
Mutable
p163 Unlike strings, lists are mutable.
# A list contains multiple values in an ordered sequence
#
# Unlike strings, list are mutable, they can be changes
numbers = [1, 2]
numbers[1] = 3
assert numbers == [1, 3]
assert numbers != [1, 2]
Concat
p167 ! You can use the + operator concatenate lists.
# To concatenate two list use + operator
a = [1, 2, 3]
b = [4, 5, 6]
c = a + b
assert c == [1, 2, 3, 4, 5, 6]
assert c != [1, 2, 7, 5, 6]
assert c != [1, 2, 3]
# To multiply a list use * operator
a = [2]
b = [2] * 4
assert b == [2, 2, 2, 2]
assert b != 8
assert b != [ [2], [2], [2], [2] ]
Slice
! The slice operator also works on lists.
# The slice operator [:] works on list
# (same as with strings)
#
# The value -1 refers to the last index in a list
word = "abcde"
assert word[:1] == "a"
assert word[1:] == "bcde"
assert word[1:3] == "bc" # 3 limit, not included
list = ["a", "b", "c", "d", "e"]
assert list[:1] != "a"
assert list[:1] == ["a"]
assert list[1:] == ["b", "c", "d", "e"]
assert list[1:3] == ["b", "c"]
assert list[-1] == "e" # last
Append
p168 ! You can append the list.
# To add an element to a list use append()
# To add a list to another list use extend()
#
# The del statement removes values at the index in a list
A = ['a', 'b', 'c']
A.append('x')
assert A != ['a', 'b', 'c']
assert A == ['a', 'b', 'c', 'x']
B = ['d', 'e']
A.extend(B)
assert A != ['a', 'b', 'c']
assert A == ['a', 'b', 'c', 'x', 'd', 'e']
del A[3]
assert A == ['a', 'b', 'c', 'd', 'e']
Sorted
Display a sorted list of installed python modules.
"""Display all installed python modules
CLI commands examples:
pip list
pip list --outdated
pip show pyperclip
pip install pyperclip
"""
import pkg_resources
pkgs = pkg_resources.working_set
pkgs = sorted(['%s \t %s' % (k.key, k.version) for k in pkgs])
print('\n'.join(pkgs))
# ...
# ufw 0.36
# unattended-upgrades 0.1
# urllib3 1.25.8
# usb-creator 0.3.7
# wadllib 1.3.3
# wheel 0.34.2
# xkit 0.0.0
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