adii1823
102 lines
2.4 KiB
Python
102 lines
2.4 KiB
Python
# lists.py
|
|
|
|
|
|
# creation
|
|
>>> [] # empty list
|
|
[]
|
|
>>> list() # same as []
|
|
[]
|
|
>>> [1, 2, 3] # as with tuples, items are comma separated
|
|
[1, 2, 3]
|
|
>>> [x + 5 for x in [2, 3, 4]] # Python is magic
|
|
[7, 8, 9]
|
|
>>> list((1, 3, 5, 7, 9)) # list from a tuple
|
|
[1, 3, 5, 7, 9]
|
|
>>> list('hello') # list from a string
|
|
['h', 'e', 'l', 'l', 'o']
|
|
|
|
|
|
# main methods
|
|
>>> a = [1, 2, 1, 3]
|
|
>>> a.append(13) # we can append anything at the end
|
|
>>> a
|
|
[1, 2, 1, 3, 13]
|
|
>>> a.count(1) # how many `1` are there in the list?
|
|
2
|
|
>>> a.extend([5, 7]) # extend the list by another (or sequence)
|
|
>>> a
|
|
[1, 2, 1, 3, 13, 5, 7]
|
|
>>> a.index(13) # position of `13` in the list (0-based indexing)
|
|
4
|
|
>>> a.insert(0, 17) # insert `17` at position 0
|
|
>>> a
|
|
[17, 1, 2, 1, 3, 13, 5, 7]
|
|
>>> a.pop() # pop (remove and return) last element
|
|
7
|
|
>>> a.pop(3) # pop element at position 3
|
|
1
|
|
>>> a
|
|
[17, 1, 2, 3, 13, 5]
|
|
>>> a.remove(17) # remove `17` from the list
|
|
>>> a
|
|
[1, 2, 3, 13, 5]
|
|
>>> a.reverse() # reverse the order of the elements in the list
|
|
>>> a
|
|
[5, 13, 3, 2, 1]
|
|
>>> a.sort() # sort the list
|
|
>>> a
|
|
[1, 2, 3, 5, 13]
|
|
>>> a.clear() # remove all elements from the list
|
|
>>> a
|
|
[]
|
|
|
|
|
|
# extending
|
|
>>> a = list('hello') # makes a list from a string
|
|
>>> a
|
|
['h', 'e', 'l', 'l', 'o']
|
|
>>> a.append(100) # append 100, heterogeneous type
|
|
>>> a
|
|
['h', 'e', 'l', 'l', 'o', 100]
|
|
>>> a.extend((1, 2, 3)) # extend using tuple
|
|
>>> a
|
|
['h', 'e', 'l', 'l', 'o', 100, 1, 2, 3]
|
|
>>> a.extend('...') # extend using string
|
|
>>> a
|
|
['h', 'e', 'l', 'l', 'o', 100, 1, 2, 3, '.', '.', '.']
|
|
|
|
|
|
# most common operations
|
|
>>> a = [1, 3, 5, 7]
|
|
>>> min(a) # minimum value in the list
|
|
1
|
|
>>> max(a) # maximum value in the list
|
|
7
|
|
>>> sum(a) # sum of all values in the list
|
|
16
|
|
>>> from math import prod
|
|
>>> prod(a) # product of all values in the list
|
|
105
|
|
>>> len(a) # number of elements in the list
|
|
4
|
|
>>> b = [6, 7, 8]
|
|
>>> a + b # `+` with list means concatenation
|
|
[1, 3, 5, 7, 6, 7, 8]
|
|
>>> a * 2 # `*` has also a special meaning
|
|
[1, 3, 5, 7, 1, 3, 5, 7]
|
|
|
|
|
|
# cool sorting
|
|
>>> from operator import itemgetter
|
|
>>> a = [(5, 3), (1, 3), (1, 2), (2, -1), (4, 9)]
|
|
>>> sorted(a)
|
|
[(1, 2), (1, 3), (2, -1), (4, 9), (5, 3)]
|
|
>>> sorted(a, key=itemgetter(0))
|
|
[(1, 3), (1, 2), (2, -1), (4, 9), (5, 3)]
|
|
>>> sorted(a, key=itemgetter(0, 1))
|
|
[(1, 2), (1, 3), (2, -1), (4, 9), (5, 3)]
|
|
>>> sorted(a, key=itemgetter(1))
|
|
[(2, -1), (1, 2), (5, 3), (1, 3), (4, 9)]
|
|
>>> sorted(a, key=itemgetter(1), reverse=True)
|
|
[(4, 9), (5, 3), (1, 3), (1, 2), (2, -1)]
|