Python несколько трюков

(1) Swapping values

x, y = 1, 2
print(x, y)
x, y = y, x
print(x, y)

(2) Combining a list of strings into a single one

sentence_list = ["my", "name", "is", "George"]
sentence_string = " ".join(sentence_list)
print(sentence_string)
fruits = ['apple', 'mango', 'orange']
print(', '.join(fruits))

numbers = [1, 2, 3, 4, 5]
print(', '.join(map(str, numbers)))

items = [1, 'apple', 2, 3, 'orange']
print(', '.join(map(str, items)))
row = [100, "android", "ios", "blackberry"]print(', '.join(str(x) for x in row))print(*row, sep=', ')

(3) Splitting a string into a list of substrings

sentence_string = "my name is George"
sentence_string.split()
print(sentence_string)

(4) Initialising a list filled with some number

[0]*1000 # List of 1000 zeros 
[8.2]*1000 # List of 1000 8.2's

(5) Merging dictionaries

x = {'a': 1, 'b': 2}
y = {'b': 3, 'c': 4}
z = {**x, **y}

(6) Reversing a string

name = "George"
name[::-1]

(7) Returning multiple values from a function

def get_a_string():
    a = "George"
    b = "is"
    c = "cool"
    return a, b, c
sentence = get_a_string()
(a, b, c) = sentence

(8) List comprehension

a = [1, 2, 3]
b = [num*2 for num in a] # Create a new list by multiplying each                                 element in a by 2

(9) Iterating over a dictionary

m = {'a': 1, 'b': 2, 'c': 3, 'd': 4} 
for key, value in m.items():
    print('{0}: {1}'.format(key, value))

(10) Iterating over list values while getting the index too

m = ['a', 'b', 'c', 'd']
for index, value in enumerate(m):
    print('{0}: {1}'.format(index, value))

(11) Initialising empty containers

a_list = list()
a_dict = dict()
a_map = map()
a_set = set()

(12) Removing useless charaters on the end of your string

name = "  George "
name_2 = "George///"
name.strip() # prints "George"
name_2.strip("/") # prints "George"

(13) Find the most frequent element in a list

test = [1, 2, 3, 4, 2, 2, 3, 1, 4, 4, 4]
print(max(set(test), key = test.count))
### Use Counterfrom collections import Counter
num_lst = [1, 1, 2, 3, 4, 5, 3, 2, 3, 4, 2, 1, 2, 3]cnt = Counter(num_lst)print(dict(cnt))
# first 2 most occurrenceprint(dict(cnt.most_common(2)))
str_lst = ['blue', 'red', 'green', 'blue', 'red', 'red', 'green']print(dict(Counter(str_lst)))

(14) Check the memory usage of an object

import sys
x = 1
print(sys.getsizeof(x))

(15) Convert a dict to XML 

from xml.etree.ElementTree import Elementdef dict_to_xml(tag, d):
    '''
    Turn a simple dict of key/value pairs into XML
    '''
    elem = Element(tag)
    for key, val in d.items():
        child = Element(key)
        child.text = str(val)
        elem.append(child)
    return elem

(16) Sort Dictionary

from operator import itemgetter

d = {'a': 10, 'b': 20, 'c': 5, 'd': 8, 'e': 5}# sort by value
print(sorted(d.items(), key=lambda x: x[1]))# sort by value
print(sorted(d.items(), key=itemgetter(1)))# sort by key
print(sorted(d.items(), key=itemgetter(0)))# sort by value and return keys
print(sorted(d, key=d.get))

  (17) Remove Duplicates From List

lst = [7, 3, 3, 5, 6, 5]

# removes duplicates but does not preserves the list order
no_dups = list(set(lst))
print(no_dups)

# removes duplicates and preserves the list order
from collections import OrderedDict
no_dups = list(OrderedDict.fromkeys(lst).keys())
print(no_dups)

(18) Merge Dictionaries

d1 = {'a': 1}
d2 = {'b': 2}print(dict(d1.items() | d2.items()))
print({**d1, **d2})d1.update(d2)
print(d1)

(19) Loop Over Multiple Lists at the Same Time

colors = ["red", "green", "yellow", "blue"]
codes = [1, 2, 3, 4]
for color, code in zip(colors, codes):
    print(f"{code}, {color}")# another behavior
from itertools import zip_longestcolors = ["red", "green", "yellow", "blue"]
codes = [1, 2, 3, 4, 5, 6]for color, code in zip_longest(colors, codes):
    print(f"{code}, {color}")for color, code in zip_longest(colors, codes, fillvalue='Nothing'):
    print(f"{code}, {color}")