老司机都知道的Python语法小技巧

写在前面---Python的优势在于

1.与主要平台和操作系统兼容
2.许多开源框架和工具
3.可读且可维护的代码
4.强大的标准库
5.标准测试驱动的开发

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• 话不多说了，本文是第二部分，将讲简单的列出几条日常工作中使用Python可能会用到的语法小技巧，希望会对你的工作有所帮助 just enjoy！
  第一部分是：老司机都知道的Python语法小技巧 (一)

14.列表中元素出现的个数

# 伊洛Yiluo
# https://yiluotalk.com
>>> from collections import Counter
>>> list = [1,2,3,4,5,1,2,3,4,5,6]
>>> count = Counter(list)
>>> count
Counter({1: 2, 2: 2, 3: 2, 4: 2, 5: 2, 6: 1})

15.列表中查找出现最多的元素

# 伊洛Yiluo
# https://yiluotalk.com
>>> def most_frequement(list):
...     return max(set(list), key = list.count)
...
>>> number = [1,2,3,4,5,6,5,5,5,5,5]
>>> most_frequement(number)
5

16. 将角度从度转换为弧度

# 伊洛Yiluo
# https://yiluotalk.com
>>> import math
>>> def degrees_to_radians(deg):
...     return (deg * math.pi) / 180
>>> degrees_to_radians(90)
1.5707963267948966

17. 计算执行一段代码所花费的时间(非装饰器)

# 伊洛Yiluo
# https://yiluotalk.com
import time
start_time = time.time()
a, b = 10, 20
c = a + b
end_time = time.time()
time_taken = (end_time- start_time)*(10**6)
print('耗时', time_taken)


output
耗时 2.1457672119140625

Process finished with exit code 0

18. 字符串去重

# 伊洛Yiluo
# https://yiluotalk.com
>>> string = "aabbccddeeffgg"
>>> unique = set(string)
>>> unique
{'a', 'f', 'b', 'g', 'c', 'e', 'd'}
>>> new_string = ''.join(unique)
>>> new_string
'afbgced'

19. 使用lambda表达式

# 伊洛Yiluo
# https://yiluotalk.com
>>> x = lambda a, b, c :a + b + c
>>> print(x(1, 2, 3))
6

20. 使用 filter

# 伊洛Yiluo
# https://yiluotalk.com
>>> arr = [1, 2, 3, 4, 5]
>>> arr = list(filter(lambda x : x%2 == 0, arr))
>>> print(arr)
[2, 4]

21. 列表

# 伊洛Yiluo
# https://yiluotalk.com
>>> number = [1, 2, 3]
>>> squares = [number**2 for number in number]
>>> print(squares)
[1, 4, 9]

22. 切片

# 伊洛Yiluo
# https://yiluotalk.com
>>> def rotate(arr, d):
...     return arr[d:] + arr[:d]
...
>>> arr = [1,2,3,4,5]
>>> arr = rotate(arr, 2)
>>> print(arr)
[3, 4, 5, 1, 2]

23. 链式函数

# 伊洛Yiluo
# https://yiluotalk.com
>>> def subtract(a, b):
...     return a - b
...
>>> def add(a, b):
...     return a + b
...
>>> def subtract(a, b):
...     return a - b
...
>>> a, b = 5, 10
>>> print((subtract if a > b else add)(a, b))
15
>>> a, b = 10, 5
>>> print((subtract if a > b else add)(a, b))
5

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