PROGRAMMING

  minte9
learningjourney




S R Q

Mutable

p163 Unlike strings, lists are mutable.
 
"""Lists are mutable
A list contains multiple values in an ordered sequence
"""

A = [1, 2]; A[1] = 3

assert A == [1, 3]
assert A != [1, 2]

print('Tests passed')

Concat

p167 You can use the + operator concatenate lists.
 
"""To concatenate two list use + operator
To multiply a list use * operator
"""

A = [1, 2] + [3,4]
B = [9] * 4
C = A * 2

assert A == [1, 2, 3, 4]
assert B == [9, 9, 9, 9]
assert C == [1, 2, 3, 4, 1, 2, 3, 4]

print('Tests passed')

Slice

The slice operator also works on lists.
 
""" Slice operator [:] works on list, as with strings
The value -1 refers to the last index in a list
"""

a = "abcde"

assert a[:1]  == "a"
assert a[1:]  == "bcde"
assert a[1:3] == "bc" # limit 3 not included

A = [1, 2, 3, 4, 5]

assert A[:1]   != 1
assert A[:1]   == [1]
assert A[1:]   == [2, 3, 4, 5]
assert A[1:3]  == [2, 3] # limit 3 not included
assert A[-1]   == 5
assert A[-1:]  == [5] # last

print('Tests passed')

Append

p168 You can append the list.
 
"""List append() extend()

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', 'x', 'd', 'e']
assert A == ['a', 'b', 'c', 'd', 'e']

print('Tests passed')

Sorted

Display a sorted list of installed python modules.
 
"""Display all installed python modules
CLI 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    pip list --outdated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

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