xdc_git_python_20210511/python_base/note/Python_day03_昨日回顾.txt

Python_day03_01_昨日回顾.txt

1. 变量

s = 'qf'
先创建对象，之后把名字分配给这个对象。
等号右边的对象先被创建或者被获取

a = b = c = 1

a, d = 1,2


a = 1
b = 2

a ---2
b ---1

c = a

a = b

b = c

a, b = b, a  # a, b = 2, 1
a --- 2
b --- 1

2. 运算符

n = 1

n += 1
n += 2

10 // 3

10 % 2

10 % 3

3.逻辑运算符

and

or

not 

in

4. 比较运算符
==
>
<
>=
<=
!=

5. 
if ...:
   pass


if ...:
   pass
else:
   pass

for i in ...:
     pass


while  ...:
    pass


6. 字符串

s = 'www.qfduc.ocm'

s = s.split('.', 1)[0]


反向切割
s.rsplit()

开头查找
s.startswith()
结尾查找
s.endswith()
移除字符串头尾指定的字符串（默认为空格或换行符）
s.strip()

input(">>:").strip()


----------------


while True:
   ...

else:
   pass

for i in ...:
   ...

else:
   pass


字符串的替换
s.replace()
s.replace(old, new[, max])
返回字符串中的old（旧字符串）替换成new（新字符串）后生成的新字符串，如果指定第三个参数max，则替换不超过max次。


any

all


not ()


list

tuple

dict

set