字符串操作指南-优快云博客

字符串

1.什么是字符串

用引号引起来的一串字符
用引号来创建字符串。
- 单引号
- 双引号
- 三单引号
- 三双引号

name = "HangZhou"
area = "GongShu"
history = "1500"
famous_person = """苏轼，法海"""
capticalof = '''吴越,南宋'''


print(type(name),type(area),type(history),type(famous_person),type(capticalof))

sent = "I'm Lilei"
sent2 = 'He is my brother,he said'
print(sent)
print(sent2)
#单引号和双引号使用时需要注意匹配关系，且不能换行
#若需要换行，使用三单引号或者三双引号
ex = '''这是第一行
        这是第二行
     换行记得三单三双'''

2.字符串的运算及常见操作

2.1拼接

拼接基于同一种数据类型

a = "hello"
b = ", python"
print(a+b)

a = ["类型相同"]
b = ["，才能拼接"]
print(a+b)

2.2重复

a = "hello"
print(a * 3)

2.3索引（偏移） [] , 切片[:],[::]

sr = "Python"
for i in sr:
    print(i,end=" ")

sr = "Python"
print(len(sr))
a = len(sr)
for i in range(a):
    print(sr[i],end=" ")

     #012345678901234567890123456789
sr = "life is short, you need python."
print(len(sr))
print(sr[0:5])   #life
#取01234  5之前
print(sr[1:4:2]) #ie   步长2  取13
print(sr[1::2])  #iei hr,yune yhn 135791357913579

2.4大小写转换

函数	功能
.lower()	转小写
.upper()	转大写
.swapcase()	大小写转换
.title()	转为标题的形式
.capitalize()	首字母大写

sr = "Life Is Short, You Need Python."
print(sr.upper())
print(sr.lower())
print(sr.swapcase())
print(sr.title())
print(sr.capitalize())
#LIFE IS SHORT, YOU NEED PYTHON.
#life is short, you need python.
#lIFE iS sHORT, yOU nEED pYTHON.
#Life Is Short, You Need Python.
#Life is short, you need python.

demo: 验证码确认

#验证码确认
sr = input("输入你看到的验证码,不区分大小写:")
srr = "LIFE"
if sr.upper() == srr:
    print("输入正确")
else:
    print("错误")

三次验证机会该如何做

2.5字符串的格式输出对齐

.center([len],[填充符号]) ,左对齐

sr = "Life Is Short, You Need Python."
print(sr.center(41,'#'))
print(sr.ljust(41,'$'))
print(sr.rjust(41,'^'))
print(sr.zfill(41))     居右对齐，默认填充0

#####Life Is Short, You Need Python.#####
Life Is Short, You Need Python.$$$$$$$$$$
^^^^^^^^^^Life Is Short, You Need Python.
0000000000Life Is Short, You Need Python.

2.6删除指定字符

.strip() 删除开头结尾指定符号若不给参数则默认删除\n\t等符号

.lstrip()

.rstrip()

sr = "#####Life Is Short, You Need Python.#####"
print(sr.strip('#'))

Life Is Short, You Need Python.

sr = "\n#####Life Is Short, You Need Python.#####\n"
print(sr.strip())
#####Life Is Short, You Need Python.#####

2.7计数

.count()

      012345678901234567890123456789
sr = "Life Is Short, You Need Python."
print(sr.count('o',9,17))

#sr.count('统计元素',[start],[end]) 统计该元素在start，end-1出现的次数

2.8字符串搜索定位和替换

.find(),查找元素并返回第一次出现的元素索引值，若不存返回 -1

.index()查找元素并返回第一次出现的元素索引值，若不存报错

.rindex()从右往左查找

.replace([现有],[替新],[数量]) 默认数量值为1

      012345678901234567890123456789
sr = "Life Is Short, You Need Python."
print(sr.find('o',9,25))         #   10
#若不存在 返回值 #  -1
      012345678901234567890123456789
sr = "Life Is Short, You Need Python."
print(sr.index('0',9,25))        #  10
#若不存在 则报错

sr = "Life Is Short, You Need Python."
print(sr.replace('Python','Money'))
#  Life Is Short, You Need Money.

sr = "Life Is Short, You Need Python."
print(sr.replace('t','T',1))
# Life Is ShorT, You Need Python.

2.9字符串条件判断

.isalnum() , 判断字符串有字母或者数字组成

.isalpha() , 仅有字母

.isgidit() , 仅有数字

a = "afwtg35376dae"
b = "abc"
c = "123"
print(a.isalnum())
print(b.isalpha())
print(c.isdigit())

2.10制表符的转化

.expandtabs()

2.11字符串的分割变换

.join() , 将指定字符插入到元素之间

.split() , 以指定字符分割字符串并去除该字符

.partition() , 以指定字符分割字符串并保留该字符

#能快速将一个list变为str
li = ['i','love','python']
print(' '.join(li))      #i love python

#以指定字符将字符串切割成列表
sr = "Life Is Short,You Need Python."
print(sr.split('o',2))     #['Life Is Sh', 'rt,Y', 'u Need Python.']

#切割为元组
print(sr.partition('o')) #只能切割一次 ('Life Is Sh', 'o', 'rt,You Need Python.')

2.12ASCII值和字符的转换

chr() digit —> alpha

ord() alpha —> digit

for i in range(ord('a'),ord('z')+1):
    print(chr(i),end=' ')

随机生成四位由数字，大小写英文字母组成的验证码

VCode = ''
import string
#dir(string)
#print(dir(string))
import random
#print(string.printable)
#print(string.printable.find('Z'))

#for i in range(4):
#VCode += random.choice(string.printable[0:62])
#print(VCode)
VCode = random.sample(string.printable[0:62],4)
print(''.join(VCode))