PYTHON 技巧

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

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

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

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

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

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[5,2]*4

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"hello"*3

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

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

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

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

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

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

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

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

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

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

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#python3 -m http. server

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

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

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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))

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

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

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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

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

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

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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

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

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

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

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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"))

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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])

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

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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])

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

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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

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

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

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

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

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

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