python的骚操作

1.查找列表中出现频率最高的值

# 方法一
a = [1, 1, 2, 3, 4, 4, 4, 5, 5, 6]
max(a, key = a.count)

# 方法二
from collections import Counter
cnt = Counter(a)
print(cnt.most_common(3))

2.检查两个字符串是不是由相同字母 不同顺序组成

from collections import Counter
Counter(str1) == Counter(str2)

3.转置二维数组

list(zip(*[['a', 'b', 'a'], ['c', 'd', 'c'], ['e', 'f', 'e']]))

4.链式比较

b = 6
print(4< b < 7)
print(1 == b < 20)

5.for else

a = [1, 2, 3, 4, 5]
for i in a:
    if i == 0:
        break
else:
    print('没有执行break')

6.合并字典

dict1 = {'a': 1, 'b': 2}
dict2 = {'c': 3, 'd': 4}
# 方法1
{**dict1, **dict2}
# 方法2
dict(dict1.items() | dict2.items())
# 方法3
dict1.update(dict2)

7.list中的元素，两两组合

from itertools import combinations, permutations
a = [1, 2, 3]

cc = list(combinations(a, 2))
>>> [(1, 2), (1, 3), (2, 3)]

dd = list(permutations(a, 2))
>>> [(1, 2), (1, 3), (2, 1), (2, 3), (3, 1), (3, 2)]

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