7 str字符串的内置函数

# def replace(self, old, new, count=None)
print("***replace替换***")
print("jasonjasonjason".replace("a","bb")) # jbbsonjbbsonjbbson
print("jasonjasonjason".replace("a","bb",1)) # jbbsonjasonjason
print("jasonjasonjason".replace("a","bb",2)) # jbbsonjbbsonjason

# 将单词格式化为：首字母大写
v1 = str1.capitalize()
print(v1) # Alex

# 将字符格式化为：全小写
# casefold功能更强大，会将法语等其他语言的字符也全部小写
v2 = str1.casefold() # alex
v3 = str1.lower() # alex
print(v2)
print(v3)

# 转小写
# 判断是否全小写
print("***章节：小写***")
print("LaSa".islower()) # False
print("LaSa".lower()) # lasa
print("LaSa".lower().islower()) # True

# ***章节：大写***
# 转大写
# 判断是否全大写
print("***章节：小写***")
print("LaSa".isupper()) # False
print("LaSa".upper()) # LASA
print("LaSa".upper().isupper()) # True

# def center(self, width, fillchar=None)
# （居中）格式化固定宽度，并设定填充字符
v4 = str1.center(20, "-")
print(v4) # --------aLex--------

# ljust(self, width, fillchar=None) 左起，右填充
# rjust(self, width, fillchar=None) 右起，左填充
print("填充")
print("alex".ljust(20,"*")) # alex****************
print("alex".rjust(20,"*")) # ****************alex

# 从start到end之间，统计子序列总数
# sub： 子序列，即子字符串
# start: 起始位置
# end: 结束
string1 = ‘aLEx is a woman, who is a nurse‘
v5 = string1.count(‘is‘)
print(v5)

str1 = ‘aLex‘
a = str1.startswith("a") # True
print(a)
e = str1.endswith("ex") # True
print(e)

# 从[start,end)找子序列的第一个位置索引
# 无该子序列，则返回-1
test = "alexalex"
v = test.find(‘ex‘,0,8) # 2
print(v)

# 从[start,end)找子序列的第一个位置索引
# index找不到子序列，则报异常
v1 = test.index(‘ex‘)
print(v1)

# 字符串中引用变量：{name}和{num}
test = ‘i am {name}, age {num}‘
print(test) # i am {name}, age {num}
# 为字符串中变量赋值
v = test.format(name=‘alex‘, num=19)
print(v) # i am alex, age 19

# 字符串中引用变量：{0}和{1}
test = ‘i am {0}, age {1}‘
print(test) # i am {0}, age {1}

# 为字符串中变量赋值
v = test.format(‘alex‘, 19)
print(v) # i am alex, age 19

# 字符串中引用变量：{name}和{num}
test = ‘i am {name}, age {num}‘

print(test) # i am {name}, age {num}

# 为字符串中变量赋值
v = test.format(name=‘alex‘, num=19)
print(v) # i am alex, age 19

v1 = test.format_map({"name":‘alex‘, "num":19})
print(v1) # i am alex, age 19

test1 = "usdfd839"
# 是否字母和数字组成的字符串
v = test1.isalnum() # True
v1 = test1.isalpha() # False， 是否为字母序列
strTest = "abddfj"
s1 = strTest.isalpha() # True， 是否为字母序列

numTest = "123"
v1 = numTest.isdecimal() # True，是否键盘数字
v2 = numTest.isdigit() # True，包括②等数字
print("②".isdigit()) # True
print("贰".isdigit()) # False
print("贰壹②".isnumeric()) # True
print("Ⅱ".isdigit()) # False
print("Ⅱ".isdecimal()) # False

# def expandtabs(self, tabsize: int = 8)
# expandtabs，制表: \n断句 \t对齐
# tabsize：长度，使用空格填充对齐
test2 = "username\temail\tpassword\nlaiying\tying@qq.com\t123\nlaiying\tying@qq.com\t123\nlaiying\tying@qq.com\t123"
v2 = test2.expandtabs(20)
print(v2)

# 反转大小写
print("aLex".swapcase()) # AlEX
print("ALex".swapcase()) # alEX

# 是否正确的标识符：即是否正确命名规则，也包括关键字def class
print("def".isidentifier()) # True
print("class".isidentifier()) # True
print("_123".isidentifier()) # True
print("123".isidentifier()) # False
print("userName".isidentifier()) # True

# isprintable() 是否全部为可见字符
# 不可见字符: \t \n \001
print("是否全部为可见字符")
print("dfsdifhfd337&&***//".isprintable()) # True
print("dfsdi\nfhfd337\001&&***//".isprintable()) # False
print("dfsdifhfd337\001&&***//".isprintable()) # False

# isspace()是否全部为空格
print(" ".isspace()) # True
print(" \t".isspace()) # True
print(" \001".isspace()) # False
print(" \n".isspace()) # True

print("是否为标题（只能判断英文）")
print("Process finished with exit code 0".istitle()) # False
print("Process finished with exit code 0".title()) # Process Finished With Exit Code 0
print("Process finished with exit code 0".title().istitle()) # True

print("将字符串中的每一个元素按指定分隔符进行拼接")
print(" ".join("你是风儿我是沙")) # 你 是 风 儿 我 是 沙
print("_".join("你是风儿我是沙")) # 你_是_风_儿_我_是_沙

# 拼接字符串元素
v = "_".join("abcde")

# 拼接列表元素
v = "_".join([‘jason‘, ‘rose‘]) # jason_rose

print("去除空格(包括\n \t) 和 去除指定字符序列")
print(" haha ".lstrip())
print(" haha ".rstrip())
print(" haha ".strip())
print(" haha ".strip())
print("\n haha ".strip())
print("dfhahadf".lstrip(‘df‘)) # hahadf
print("dfhahadf".rstrip(‘df‘)) # dfhaha
print("dfhahadf".strip(‘df‘)) # haha

print("dfhahadf".rstrip(‘9adf‘)) # dfhah
print("dfhahadf".rstrip(‘9adfah‘)) # 全删：从右开始删adf，再删ah，再删h，再删df

# 构建映射表：tr_tab = str.maketrans("abcdef","123456")
# 执行映射替换：srcStr.translate(tr_tab)
# 将对应位置的字符进行替换
# abcdef
# 123456
# 构建映射表：str.maketrans("abcdef","123456")
# 执行映射替换：srcStr.translate(tr_tab)
tr_tab = str.maketrans("abcdef","123456")
strList = "fasdfjbaczxjivewr;oifajmewirkcvxweafo;dsapojnsafdk"
tranList = strList.translate(tr_tab)
print(tranList) # 61s46j213zxjiv5wr;oi61jm5wirk3vxw516o;4s1pojns164k

# 分隔
#
print("***分隔***")
print("testadfkajoeiawjfs".partition("a")) # (‘test‘, ‘a‘, ‘dfkajoeiawjfs‘)
print("testadfkajoeiawjfs".rpartition("a")) # (‘testadfkajoei‘, ‘a‘, ‘wjfs‘)

print("testadfkajoeiawjfs".split("a")) # [‘test‘, ‘dfk‘, ‘joei‘, ‘wjfs‘]
print("testadfkajoeiawjfs".split("a",1)) # [‘test‘, ‘dfkajoeiawjfs‘]
print("testadfkajoeiawjfs".split("a",2)) # [‘test‘, ‘dfk‘, ‘joeiawjfs‘]
print("testadfkajoeiawjfs".rsplit("a",2)) # [‘testadfk‘, ‘joei‘, ‘wjfs‘]
print("testadfkajoeiawjfs".split("a",6)) # [‘test‘, ‘dfk‘, ‘joei‘, ‘wjfs‘]
print("testadfkajoeiawjfs".rsplit("a",6)) # [‘test‘, ‘dfk‘, ‘joei‘, ‘wjfs‘]

print(v) # range(0, 100)

in_str = "33+88"
v1, v2 = in_str.split(‘+‘)
print(in_str, ‘=‘, int(v1) + int(v2)) # 121

# 分隔，分页，换行
# def splitlines(self, keepends=None) : keepends是否保留换行符
print("fdahsf\niensdka\npoieafl\nfewascsakdn".splitlines()) # [‘fdahsf‘, ‘iensdka‘, ‘poieafl‘, ‘fewascsakdn‘]
print("fdahsf\niensdka\npoieafl\nfewascsakdn".splitlines(False)) # [‘fdahsf‘, ‘iensdka‘, ‘poieafl‘, ‘fewascsakdn‘]
print("fdahsf\niensdka\npoieafl\nfewascsakdn".splitlines(True)) # [‘fdahsf\n‘, ‘iensdka\n‘, ‘poieafl\n‘, ‘fewascsakdn‘]

print(len("first")) # 5

# Python3: len获取当前字符串中有几个字符
# Python27：len获取字符串占几个字节，utf8单个中文3字节
print(len("张五常")) # 3

name = ‘abcdef‘   

print(name[0]) # a   
print(name[1]) # b   
print(name[-2])  //负数表示从右边开始：-2表示右边第二个

# -*- coding:utf-8 -*-
‘‘‘
python中下标从 0 开始
‘‘‘
name = ‘abcdef‘
print(name[0:3]) # 取 下标0~2 的字符 abc
print(name[:3]) # 取 下标0~2 的字符 abc

print(name[0:5]) # 取 下标为0~4 的字符 abcde
print(name[3:5]) # 取 下标为3、4 的字符 de

print(name[2:]) # 取 下标为2开始到最后的字符 cdef
print(name[1:-1]) # 取 下标为1开始 到 最后第2个 之间的字符 bcde

print(name[1:-1:2]) # 取 下标为1开始 到 最后第2个之间[1,-1)从前往后步长为2 返回 bd
print(name[::2]) # 取头-尾间的字符，步长为2 ace

print(name[5:1:2]) # 返回空
print(name[5:1:-2]) # [5,1)从后往前步长为-2 返回 fd
print(name[1:5:2]) # [1,5)从前往后步长为2 返回 bd
print(name[1:7:2]) # [1,7)从前往后步长为2 返回 bdf
print(name[1:10:2]) # [1,10)从前往后步长为2 返回 bdf

c_str = "索引，下标，获取字符串中的子串"
index = 0
print("===while===")
while index < len(c_str):
v = c_str[index]
print(v)

index += 1
print("====while end===")

print("***for***")
for f_v in c_str:
print(f_v)

print("***for end***")