python3学习笔记（一）

【本节知识点】：
      字符串输出
      replace
      格式化 %s   {}  format
      字符串切片

1、字符串替换输出：

>>> a = 100
>>> b = 300
>>> c = a * b
>>> print(c)
30000
// 重复3次
>>> a = "abc"
>>> b = 3
>>> c = b * a
>>> print(c)
abcabcabc
//使用replace
>>> a = "hello world"
>>> b = "O"
>>> c = a.replace("l", b)
>>> print(c)
heOOo worOd

2、字符串格式化输出：

003.jpg

>>> a = "hello%sworld" % "   "
>>> print(a)
hello   world
>>>
>>> a = "adafsafas%s999999" % "HHHHHHHHH"
>>> print(a)
adafsafasHHHHHHHHH999999
>>>
>>> b = "5 + 100 = {}".format(105)
>>> print(b)
5 + 100 = 105
>>>
>>> c = "happy birthday{}".format("to you!")
>>> print(c)
happy birthdayto you!
>>>

3、字符串切片

003.jpg

>>> a = "You are my good friend"
>>> la = len(a)
>>> print(la)
22
>>> print(a[1])       ##place 2
o
>>> print(a[0])         ##place 1
Y
######字符串包前不包后##########
>>> print(a[4:8])       ##place 4-8  
are
>>> print(a[:3])          ##place 0-3
You
>>> print(a[-7:])          ##place right 1-7
 friend
>>> print(a[-6:])      ##place right 1-6
friend
>>>
···