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  • Python学习日记(一) String函数使用

    s = "abcaDa a"
    s2 = "123a abc ABCSAa s "
    s3 = "	as 		b123"
    s4 = '    &abc123 c ##    '

    1.str.capitalize()

    将原字符串内的首字母转成大写,其他部分小写,再返回新字符串

    print("s.capitalize() = {function}".format(function = s.capitalize())) 

    Output:

    s.capitalize() = Abcada a

    2.str.upper()

    将原字符串的字母转为大写

    print("s.upper() = {function}".format(function = s.upper()))

    Output:

    s.upper() = ABCADA A

    3.str.lower()

    将原字符串的字母转为小写

    print("s.lower() = {function}".format(function = s.lower()))

    Output:

    s.lower() = abcada a

    4.str.swapcase()

    将原字符串内的大写小写反转

    print("s.swapcase() = {function}".format(function = s.swapcase()))

    Output:

    s.swapcase() = ABCAdA A

    5.str.title()

    原字符串内如果有特殊字符(包括数字)连接字母,则将特殊字符后的首个英文字母转化为大写形态,并返回新字符串

    print("s2.title() = {function}".format(function = s2.title()))

    Output:

    s2.title() = 123A Abc Abcsaa S

    6.str.center()

    str.center(宽度,填充字符) 将字符串以居中的格式返回,若宽度值比len(s)小则返回原字符串,填充以从左到右为规则,填充字符的默认值为空格,值可以自己更改

    print("s2.center() = {function}".format(function = s2.center(19,'&')))
    print("s2.center() = {function}".format(function = s2.center(20,'&')))

    Output:

    #s2 = 123a abc ABCSAa s
    s2.center() = &123a abc ABCSAa s 
    s2.center() = &123a abc ABCSAa s &

    7.str.expandtabs()

    str.expandtabs(tabsize = 8) 将原字符串中 以前的字符补满8位(默认),tabsize的值从0-7即8位,在0-7中任意取值则默认tabsize = 8,此后

    往上+1,就相当于增加一个空格

    print("s3.expandtabs ={function}".format(function = s3.expandtabs()))
    print("s3.expandtabs ={function}".format(function = s3.expandtabs(0)))
    print("s3.expandtabs ={function}".format(function = s3.expandtabs(5)))
    print("s3.expandtabs ={function}".format(function = s3.expandtabs(8)))
    print("s3.expandtabs ={function}".format(function = s3.expandtabs(9)))

    Output:

    #s3 = "	as 		b123"
    s3.expandtabs =        as              b123
    s3.expandtabs =as b123
    s3.expandtabs =     as        b123
    s3.expandtabs =        as              b123
    s3.expandtabs =         as                b123

    8.String_len = len(str)

    公共方法,计算字符串的长度

    print("s2_length = {0}".format(len(s2))) 

    Output:

    s2_length = 18

    9.str.startswith()

    str.startswith(substr,strbeg,strend) 判断原字符串是否以子字符串开头 可以用切片的形式进行判断(以顾头不顾尾为原则),这里的strend要比strbeg大否则传回false 函数结果返回一个布尔值

    print("s.startswith() = {function}".format(function = s.startswith('ab')))
    print("s.startswith() = {function}".format(function = s.startswith('D',2)))
    print("s.startswith() = {function}".format(function = s.startswith('c',2,5)))
    print("s.startswith() = {function}".format(function = s.startswith('c',2,100)))

    Output:

    #s = abcaDa a
    s.startswith() = True
    s.startswith() = False
    s.startswith() = True
    s.startswith() = True

    10.str.endswith()

    str.endswith(substr,strbeg,strend) 判断字符串是否以子字符串结尾 结果返回布尔值,这里的strend要比strbeg小否则传回false 和startswith()一样要从左到右为原则

    print("s.endswith() = {function}".format(function = s.endswith('Da a')))
    print("s.endswith() = {function}".format(function = s.endswith('a',-1)))
    print("s.endswith() = {function}".format(function = s.endswith('Da a',-4)))
    print("s.endswith() = {function}".format(function = s.endswith('c',-8,-5)))
    print("s.endswith() = {function}".format(function = s.endswith('c',-7,-5)))
    print("s.endswith() = {function}".format(function = s.endswith('c',-7,-4)))
    print("s.endswith() = {function}".format(function = s.endswith('Da a',-1,6)))

    Output:

    #s = abcaDa a
    s.endswith() = True
    s.endswith() = True
    s.endswith() = True
    s.endswith() = True
    s.endswith() = True
    s.endswith() = False
    s.endswith() = False

    11.str.find()

    str.find(substr,strbeg,strend) 寻找字符串中是否存在该子字符串并返回其索引,找不到则返回-1 若同时出现相同的字符串则返回最先找到

    的子字符串索引,切片(遵循顾头不顾尾原则)

    print("s.find() = {function}".format(function = s.find('a')))
    print("s.find() = {function}".format(function = s.find('ab')))
    print("s.find() = {function}".format(function = s.find('f')))
    print("s.find() = {function}".format(function = s.find('b',-8,-5)))
    print("s.find() = {function}".format(function = s.find('b',0)))

    Output:

    s.find() = 0
    s.find() = 0
    s.find() = -1
    s.find() = 1
    s.find() = 1

    12.str.index()

    str.index(substr,strbeg,strend) 与find()的功能大致相同,但子字符串不存在于字符串中就会报错,结果返回索引

    print("s.index() = {function}".format(function = s.index('a')))
    print("s.index() = {function}".format(function = s.index('ab')))
    print("s.index() = {function}".format(function = s.index('D',-8,5)))
    print("s.index() = {function}".format(function = s.index('b',0)))

    Output:

    #s = abcaDa a
    s.index() = 0
    s.index() = 0
    s.index() = 4
    s.index() = 1

    13.str.strip()

    str.strip([chars]) 去掉字符串中首和尾的字符 默认删除的是空格 chars可以自行更改

    print("s3.strip() = {function}".format(function = s3.strip()))

    Output:

    #s3 =    as              b123
    s3.strip() = as                 b123

    14.str.rstrip()

    str.rstrip([chars]) 去掉字符串右边的字符 默认删除的是空格 返回值为删除后的新字符串

    print("s4.rstrip() = {function}".format(function = s4.rstrip()))
    print("s4.rstrip() = {function}".format(function = s4.rstrip('# c')))

    Output:

    #s4 = '    &abc123 c ##    '
    s4.rstrip() =     &abc123 c ##
    s4.rstrip() =     &abc123

    15.str.lstrip()

    str.lstrip([chars]) 去掉字符串左边的字符 默认删除的是空格 返回值为删除后的新字符串

    print("s4.lstrip() = {function}".format(function = s4.lstrip()))
    print("s4.lstrip() = {function}".format(function = s4.lstrip(' &')))

    Output:

    #s4 = '    &abc123 c ##    '
    s4.lstrip() = &abc123 c ##    
    s4.lstrip() = abc123 c ## 

    16.str.count()

    str.count(substr,start,end) start为第一个字符,这里默认为0 end未结束搜索的位置,默认为len(s) 主要功能统计字符串中某个字符出现

    的个数并返回个数

    print("s.count() = {function}".format(function = s.count('a')))
    print("s.count() = {function}".format(function = s.count('Fa')))
    print("s.count() = {function}".format(function = s.count('a',-7)))

    Output:

    #s = "abcaDa a"
    s.count() = 4
    s.count() = 0
    s.count() = 3

    17.str.split()

    str.split(substr = " ",num = s.count(str)) 主要作用分割字符串 这里的substr默认以空格分割,num为总共切割的次数,若num有数值怎分割num+1个字符串 分割后将字符串转化为list形式 substr会在分割后消失

    print("s2.split() = {function}".format(function = s2.split()))
    print("s2.split() = {function}".format(function = s2.split(' ',0)))
    print("s2.split() = {function}".format(function = s2.split('a',1)))
    print("s2.split() = {function}".format(function = s2.split('a',-1)))

    Output:

    #s2 = "123a abc ABCSAa s "
    s2.split() = ['123a', 'abc', 'ABCSAa', 's']
    s2.split() = ['123a abc ABCSAa s ']
    s2.split() = ['123', ' abc ABCSAa s ']
    s2.split() = ['123', ' ', 'bc ABCSA', ' s ']

    18.str.format()

    三种用法:

    print("s = {}|s2 = {}|s3 = {}".format(s,s2,s3))
    print("s = {0}|s2 = {1}|s3 = {2}|s = {0}|s3 = {2}".format(s,s2,s3))
    print("s = {s}{sep}s2 = {s2}{sep}s3 = {s3}".format(s = s,s2 = s2,s3 = s3,sep = '|'))

    Output:

    s = abcaDa a|s2 = 123a abc ABCSAa s |s3 =       as              b123
    s = abcaDa a|s2 = 123a abc ABCSAa s |s3 =       as              b123|s = abcaDa a|s3 =  as              b123
    s = abcaDa a|s2 = 123a abc ABCSAa s |s3 =       as              b123

    当占位符不按顺序写会报错 tuple index out of range

    19.str.replace()

    s.replace(old,new,max) old为将被替换的字符串,new为替换old的字符串,max为替换次数将字符串进行替换,若old未存在原字符串内则返回原

    字符串

    print("s.replace() = {function}".format(function = s.replace('ac','A')))
    print("s.replace() = {function}".format(function = s.replace('a','A')))
    print("s.replace() = {function}".format(function = s.replace('a','A',2)))

    Output:

    #s = "abcaDa a"
    s.replace() = abcaDa a
    s.replace() = AbcADA A
    s.replace() = AbcADa a

    20.is函数

      str.isalnum()  #判断是否由数字或字母组成

      str.isalpha()    #判断是否含有字母

      str.isdecimal()  #判断是否含有十进制数字

      str.isdigit()  #判断是否含有数字

      str.islower()  #判断是否含有小写字母

      str.isupper()  #判断是否含有大写字母

      str.isnumeric()  #判断是否只包含数字字符

      str.isspace()  #判断是否只含有空格

      str.istitle()  #判断是否经过title()函数处理过后的标题

    21.join()

    str.join(sequence)  sequence为要连接的元素序列,函数作用是将指定字符串与原字符串中每一个字符一一连接

    s = 'alex'
    print('&&'.join(s)) #a&&l&&e&&x
    l = ['a','l','e','x']
    print('+'.join(l))  #a+l+e+x
    t = ('a','b')
    print('*'.join(t))  #a*b

    PS:String索引对应

     

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  • 原文地址:https://www.cnblogs.com/Fantac/p/11192076.html
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