a=1
b=2
a,b=b,a
a,b

(2, 1)

a=b=c=50
a,b,c

(50, 50, 50)

a,b,c=[1,2,3]
a,b,c

(1, 2, 3)

a,*others=[1,2,3,4]
print(a)
print(*others)

1
2 3 4

a=10
if(5<a<15):
    print(a)

10

[5,2]*4

[5, 2, 5, 2, 5, 2, 5, 2]

"hello"*3

'hellohellohello'

age = 30
slogon = "牛逼" if age == 30 else "niubility"
print(slogon)

牛逼

a={"a":1}
b={"b":2}
{**a,**b}

{'a': 1, 'b': 2}

s = "i love python"
s[::-1]

'nohtyp evol i'

s = ["i", "love", "python"]
" ". join(s)

'i love python'

foo=[2,3,4,5]
for i in foo:
    if i == 0:
        break
else:
    print("未发现")

未发现

m = {x: x**2 for x in range(5)}
m

{0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

content = ["a", "b", "c", "a", "d", "c", "a"]
from collections import Counter
c = Counter(content)
c. most_common(1)

[('a', 3)]

from collections import defaultdict
d = defaultdict(list)
d['a']. append(1)
d['a']

[1]

import re
data = "hello123world"
if match:=re. search("(\d+)", data):
    num = match. group(1)
else:
    num=None
num

'123'

x=1
b=isinstance(x, (int, float))
b

True

#python3 -m http. server

lang = {"python":". py", "java":". java"}
dict(zip(lang. values(), lang. keys()))

{'. py': 'python', '. java': 'java'}

test = [1, 2, 3, 4, 2, 2, 3, 1, 4, 4, 4, 5]
max(set(test), key=test. count)

4

class MyClass(object):
    def __init__(self, name, identifier):
        self. name = name
        self. identifier = identifier
        self. set_up()
 
print(sys. getsizeof(MyClass))
 
class MyClass(object):
    __slots__ = ['name', 'identifier']
 
    def __init__(self, name, identifier):
        self. name = name
        self. identifier = identifier
        self. set_up()
 
print(sys. getsizeof(MyClass))

1064
896

i = ['a','b','c']
i. extend(['e','f','g'])
i

['a', 'b', 'c', 'e', 'f', 'g']

a = [ 1, 2, 3]
a[-1]

3

a = [0,1,2,3,4,5,6,7,8,9]
a[3:6] # 第3个到第6个之间的元素
a[:5] # 前5个元素
a[5:] # 后5个元素
a[::] # 所有元素（拷贝列表）
a[::2] # 偶数项
a[1::2] # 奇数项
a[::-1]  # 反转列表

[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

import itertools
a = [[1, 2], [3, 4], [5, 6]]
i = itertools. chain(*a)
list(i)

[1, 2, 3, 4, 5, 6]

a = ['Merry', 'Christmas ', 'Day']
for i, x in enumerate(a):
    print ('{}: {}'. format(i, x))

0: Merry
1: Christmas 
2: Day

le = [x*2 for x in range(10)]
le  # 每个数取平方
le = [x for x in range(10) if x%2 == 0]
le  # 获取偶数项

[0, 2, 4, 6, 8]

ge = (x*2 for x in range(10))
print(ge)
print(next(ge))
print(next(ge))
print(next(ge))

<generator object <genexpr> at 0x000001D693764190>
0
2
4

 nums = {n**2 for n in range(10)}
 nums

{0, 1, 4, 9, 16, 25, 36, 49, 64, 81}

d = {"1":"a"}
print('1' in d)
print(d['1'])
print(d. get("1"))
print(d. get("2"))

True
a
a
None

from functools import wraps
 
def tags(tag_name):
    def tags_decorator(func):
        @wraps(func)
        def func_wrapper(name):
            return "<{0}>{1}</{0}>". format(tag_name, func(name))
        return func_wrapper
    return tags_decorator
 
@tags("p")
def get_text(name):
    """returns some text"""
    return "Hello " + name
 
print(get_text("Python"))

<p>Hello Python</p>

def sub_dicts(d, keys):
    return {k:v for k, v in d. items() if k in keys}
sub_dicts({1:"a", 2:"b", 3:"c"}, [1,2])

{1: 'a', 2: 'b'}

d = {'a': 1, 'b': 2, 'c': 3, 'd': 4}
zip(d. values(), d. keys())
z = zip(d. values(), d. keys())
dict(z)

{1: 'a', 2: 'b', 3: 'c', 4: 'd'}

from collections import namedtuple
Point = namedtuple("Point", "x,y")
p = Point(x=1, y=2)
print(p. x)
print(p[0])
print(p. y)
print(p[1])

1
1
2
2

d = dict()
if 'a' not in d:
    d['a'] = []
d['a']. append(1)
d
d. setdefault('b',[]). append(2)
d

{'a': [1], 'b': [2]}

from collections import OrderedDict
m = OrderedDict((str(x), x) for x in range(10))
m. keys() # key 按照插入的顺序排列

odict_keys(['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'])

import heapq
a = [51, 95, 14, 65, 86, 35, 85, 32, 8, 98]
heapq. nlargest(5,a)
heapq. nsmallest(5,a)

[8, 14, 32, 35, 51]

import os
with open('foo. txt', 'w') as f:
    f. write("hello")
os. remove("foo. txt")

list_1 = ["One","Two","Three"]
list_2 = [1,2,3]
dictionary = dict(zip(list_1, list_2))
print(dictionary)

{'One': 1, 'Two': 2, 'Three': 3}

my_list = [1,4,1,8,2,8,4,5]
my_list = list(set(my_list))
print(my_list)

[1, 2, 4, 5, 8]

import calendar
print(calendar. month(2021, 1))

    January 2021
Mo Tu We Th Fr Sa Su
             1  2  3
 4  5  6  7  8  9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31

add = lambda a,b:a+b
add(1,2)

3