一些总结

1. bool()

a = bool(None)
b = bool()
c = bool({})
d = bool([])
e = bool(0)
print(a,b,c,d,e)
_____________
False False False False False

2. 字母数字转化

a = 123
b = str(a)
print(b,type(b))
123 <class 'str'>

a = "123"
b = int(a)
print(b,type(b))
————————
123 <class 'int'>

3. range()

python 2 中，一次性立即创建；

Python 3中，for循环是一个一个创建

range(0, 100, 1) 正序

range(0, 100, -1) 倒序

4. 分隔和转换

a = input("5+9输入:")
a1,a2 = a.split('+')
b1 = int(a1)
b2 = int(a2)
print(a1,type(a1),'
',a2,type(a2),'
',b1,type(b1),'
',b2,type(b2),'
',b1+b2)
——————————————————————————————————————
5+9输入:5+9
5 <class 'str'> 
 9 <class 'str'> 
 5 <class 'int'> 
 9 <class 'int'> 
 14

5. replace

a = 'abhjdlksa'
b= a.replace('s','&&&&&')
print(a,'
',b)
_______________
abhjdlksa 
 abhjdlk&&&&&a

6. 列表字符串转换

li = ['12b',123,'hjdka',897,78,2233,'o83ijfk']
s = ' '
for i in li:
    s = s + str(i)
print(s)
——————————————
12b123hjdka897782233o83ijfk