python笔记

1.
import operator
action = {
"+": operator.add,
"-": operator.sub,
"/": operator.truediv,
"*": operator.mul,
"**": pow
}
print(action['-'](50, 25)) # 25

2.检查重复元素
def all_unique(lst):
return len(lst) == len(set(lst))

x = [1,1,2,2,3,2,3,4,5,6]
y = [1,2,3,4,5]
all_unique(x) # False
all_unique(y) # True

3.重复打印字符串 N 次
n = 2;
s ="Programming"; print(s * n);
# ProgrammingProgramming

4.压缩
以下方法使用 fliter() 删除列表中的错误值（如：False, None, 0 和“”）
def compact(lst):
return list(filter(bool, lst))
compact([0, 1, False, 2, '', 3, 'a', 's', 34]) # [ 1, 2, 3, 'a', 's', 34 ]

5.python调试
python -m pdb xxx.py

6.替换内置函数
def isinstance_s(a, b):
return type(b).__name__ == b

__builtins__.__dict__['isinstance']=isinstance_s

7.打调用栈
import traceback as tb
def backtrace():
tb.print_stack()

8.字符串翻转
s==s[::-1]