一维列表展开为二维列表

  1. A = [1, 3, 4, 4, 5, 5]
  2. list(zip(*[iter(A)] * 2))
  3. """
  4. [(1, 2), (3, 4), (5, 6)]
  5. """

二维列表展开为一维列表

  1. B = [(1, 2), (3, 4), (5, 6)]
  2. import itertools
  3. print(list(itertools.chain.from_iterable(B)))
  5. """
  6. [1, 2, 3, 4, 5, 6]
  7. """

使用*访问列表中的每个元素

  1. # * 访问列表的所有元素
  2. def summation(*arg):
  3.     sum = 0
  4.     for i in arg:
  5.         sum += 1
  6.     return sum
  8. result = summation([1, 2, 4, 4])    # 这种传参方式会把列表当作可变位置参数的一项，见下文截图
  9. print(result)

image.pngimage.png

在同一行中打印多个元素

  1. print("111", '2222', end=' ')
  2. print('3333', end='\n')
  4. """
  5. 111 2222 3333
  6. """

在一行代码中合并 2 个字典

  1. first_dct = {"a": 1, "b": 2}
  2. second_dct = {"c": 3, "d": 4}
  3. print({**first_dct, **second_dct})
  5. """
  6. {'a': 1, 'b': 2, 'c': 3, 'd': 4}
  7. """

for实现死循环

  1. # iter除了可以将列表转化为迭代器，还能接受一个callable对象，和一个sentinel参数，当第一个对象返回sentinel值才结束
  2. for i in iter(int, 1):
  3.     pass

关闭异常自动关联上下文

  1. try:
  2.     print(1 / 0)
  3. except Exception as exc:
  4.     raise RuntimeError("something bad happened")
  6. """
  7. Traceback (most recent call last):
  8.   File "/home/worktests/base/descriptor_test.py", line 344, in <module>
  9.     print(1 / 0)
  10. ZeroDivisionError: division by zero
  12. During handling of the above exception, another exception occurred:
  14. Traceback (most recent call last):
  15.   File "/home/work/base/descriptor_test.py", line 346, in <module>
  16.     raise RuntimeError("something bad happened")
  17. RuntimeError: something bad happened
  18. """
  20. # 通过from 限制新异常是由哪个异常引起的
  21. try:
  22.     print(1 / 0)
  23. except Exception as exc:
  24.     raise RuntimeError("something bad happened") from exc
  26. """
  27. Traceback (most recent call last):
  28.   File "/home/work/tests/base/descriptor_test.py", line 364, in <module>
  29.     print(1 / 0)
  30. ZeroDivisionError: division by zero
  32. The above exception was the direct cause of the following exception:
  34. Traceback (most recent call last):
  35.   File "/home/workts/base/descriptor_test.py", line 366, in <module>
  36.     raise RuntimeError("something bad happened") from exc
  37. RuntimeError: something bad happened
  38. """
  40. # 使用raise ... from None 彻底关闭自动关联异常上下文
  41. try:
  42.     print(1 / 0)
  43. except Exception as exc:
  44.     raise RuntimeError("something bad happened") from None
  46. """
  47. Traceback (most recent call last):
  48.   File "/home/work/tests/base/descriptor_test.py", line 387, in <module>
  49.     raise RuntimeError("something bad happened") from None
  50. RuntimeError: something bad happened
  51. """

使用自带缓存机制

  1. from functools import lru_cache
  3. """
  4. maxsize: 最多可以缓存多少个此函数的调用结果，为None时无限制
  5. typed：为true，则不同参数类型的调用分别缓存
  6. """
  7. # @lru_cache(maxsize=1, typed=True)
  8. @lru_cache(None)
  9. def add(x, y):
  10.     print("计算结果：%s + %s" % (x, y))
  11.     return x + y
  13. print(add(2, 8))
  14. print(add(22, 8))
  15. print(add(222, 8))
  16. print(add(2, 8))
  18. # 计算结果：2 + 8
  19. # 10
  20. # 10
  21. # 10

流式读取超大文件

  1. filename = "test.py"
  2. def read_file(filename, block_size = 1024 * 8):
  3.     with open(filename, "r") as fp:
  4.         while True:
  5.             chunk = fp.read(block_size) # 设置读取多少个字符
  6.             if not chunk:
  7.                 print("已读取完毕")
  8.                 break
  9.             yield chunk
  12. res = read_file(filename=filename)
  13. print(res)  # 生成器对象
  14. for i in res:
  15.     print(i)

逗号的独特用法

  1. # 元组的转化
  2. def func():
  3.     return "test",
  5. print(func())    # ('test',)

运行代码时查看源代码

  1. # 运行代码查看源代码
  2. import inspect
  4. def add(x, y):
  5.     return x + y
  7. print("#"* 90)
  8. print(inspect.getsource(add))

字典访问不存在的key不报错

  1. # 方式一
  2. import collections
  4. profile = collections.defaultdict(int)
  6. # 使用匿名函数
  7. # profile = collections.defaultdict(lambda  : "this is default value")
  9. print(profile["a"])    # 0
  11. profile["a"] = 1
  13. print(profile["a"]) # 1
  16. # 方式二
  17. profile1 = {}
  18. print(profile1["a"]) # KeyError: 'a'
  19. print(profile1.get("a", 100)) # 100

利用any替换for循环

  1. # 利用any 替代for循环
  2. things = [2, 4, 1, 3]
  3. found = False
  4. for thing in things:
  5.     if thing == 1:
  6.         found = True
  7.         break
  8. print("found: {}".format(found))# found: True
  10. # 等同上for循环效果
  11. found_2 = any(thing == 1 for thing in things)
  12. print("found_2: {}".format(found_2))    # found_2: True

parse库-优雅解析规范的字符串

  1. from parse import parse
  3. before_data = (
  4.     'cookie=0x9816da8e872d717d, duration=298506.364s, table=0, n_packets=480'
  5.             )   
  7. print(f"before_data: {before_data}")
  8. # before_data: cookie=0x9816da8e872d717d, duration=298506.364s, table=0, n_packets=480
  10. parse_result = parse('cookie={cookie}, duration={duration}, table={table}, n_packets={n_packets}', before_data)
  11. print(f"parse_result: {parse_result}")
  12. # parse_result: <Result () {'cookie': '0x9816da8e872d717d', 'duration': '298506.364s', 'table': '0', 'n_packets': '480'}>
  14. print(f'cookie: {parse_result["cookie"]}')  # cookie: 0x9816da8e872d717d
  16. # 解析没有定义字段名字的情况
  17. before_data_2 = 'I am zaygee, 26 years old' 
  18. parse_2_result = parse("i am {}, {} years old", before_data_2)
  19. print(f"parse_2_result: {parse_2_result}")  # parse_2_result: <Result ('zaygee', '26') {}>
  21. # 解析类似字典的实例的情况
  22. parse_3_result = parse("i am {name}, {age} years old", before_data_2)
  23. print(f"parse_3_result: {parse_3_result}")  # parse_3_result: <Result () {'name': 'zaygee', 'age': '26'}>
  24. print(parse_3_result["name"])   # zaygee

根据进程名称模糊匹配获取pid

  1. import subprocess
  2. from typing import List
  5. def get_pid_by_process_name(name: str)->List[int]:
  6.     """根据进程名称grep 匹配获取pid"""
  7.     results = subprocess.Popen(['pgrep', '-f', name], stdout=subprocess.PIPE, shell=False)
  8.     response = results.communicate()[0]
  9.     return [int(pid) for pid in response.decode('utf-8').split() if response]
  12. if __name__ == '__main__':
  13.     get_pid_by_process_name(name='tongxue')