Python字符串和其常用函数

# coding:utf-8

if __name__ == '__main__':
    '''
     通过单引号定义
     通过三个单引号定义
     通过三个双引号定义
    '''

    a = 'this is string'
    b = '''this is string'''
    c = """this is string"""
    print(a, b, c)

# coding:utf-8

if __name__ == '__main__':
    '''
    string.capitalize() 将字符串首字母大写
    '''
    a = 'i am xieruixiang'
    print(a.capitalize())  # I am xieruixiang

# coding:utf-8

if __name__ == '__main__':
    '''
    string.upper() 将字符串中所有字母大写
    '''
    a = 'i am xieruixiang'
    print(a.upper())  # I AM XIERUIXIANG

# coding:utf-8

if __name__ == '__main__':
    '''
    string.lower(),string.casefold() 都能将字符串中所有字母小写
    casefold是lower的加强版
    '''
    a = 'I AM XIERUIXIANG'
    print(a.lower())  # i am xieruixiang
    print(a.casefold())  # i am xieruixiang

# coding:utf-8

if __name__ == '__main__':
    '''
    string.swapcase() 能将字符串中的大写变小写，小写变大写。两极反转
    '''
    a = 'i AM xIErUIxIANG'
    print(a.swapcase())  # I am XieRuiXiang

# coding:utf-8

if __name__ == '__main__':
    '''
    string.zfill(width) 用0填充字符串到指定width长度，如果字符串长度大于等于width则不填充
    '''
    a = 'abcdef'
    print(a.zfill(6))  # abcdef
    print(a.zfill(10))  # 0000abcdef

# coding:utf-8

if __name__ == '__main__':
    '''
    string.count(item) 统计字符串中有几个item
    '''
    a = 'abaacdef'
    print(a.count('a'))  # 3
    print(a.count('aa'))  # 1
    print(a.count('ha'))  # 0

# coding:utf-8

if __name__ == '__main__':
    '''
    string.startswith(item) 判断字符串是否以item开头
    string.endswith(item) 判断字符串是否以item结尾
    '''
    a = 'abaacdef'
    print(a.startswith('ab'))  # True
    print(a.endswith('ef'))  # False

# coding:utf-8

if __name__ == '__main__':
    '''
    string.find(item) 和 string.index(item) 都是查找item在字符串中第一次出现的位置
    string.find()找不到返回 -1
    string.index() 找不到返回错误
    所以使用string.find() 更多
    '''
    a = 'abcedefg'
    print(a.find('c'))  # 2
    print(a.index('c'))  # 2
    print(a.find('ac'))  # -1

# coding:utf-8

if __name__ == '__main__':
    '''
   zstring.strip(char) 过滤字符。char为None则过滤等价空格的字符，否则过滤char字符，从左往右过滤一边，从右往左再过滤一遍
    string.lstrip(char) 和strip() 相同，只不过该函数只从左往右过滤一遍
    string.rstrip(char) 和strip() 相同，只不过该函数只从右往左过滤一遍
    '''
    a = ' abcdefgh '
    b = '    abcdefgh     '
    c = 'aabbaa'
    print(a.strip())
    print(b.strip())
    print(c.strip('a'))  # bb
    print(c.lstrip('a'))  # bbaa
    print(c.rstrip('a'))  # aabb

# coding:utf-8

if __name__ == '__main__':
    '''
    string.replace(old,new,max) 将字符串中的old字符串替换成new字符串，替换max个，当max为None时替换全部
    '''
    a = 'abcdcdefg'
    print(a.replace('cd', 'ff'))  # abffffefg
    print(a.replace('cd', 'ff', 1))  # abffcdefg
    print(a.replace('hh', 'ff'))  # abcdcdefg

# coding:utf-8

if __name__ == '__main__':
    '''
    string.isspace() 判断字符串是否仅仅由空格字符串构成
    string.istitle() 判断所有单词的首字母是否大写
    string.isupper() 判断所有英文字母是否大写
    string.islower() 判断所有英文字母是否小写
    '''
    a = '     a    '
    space = '       '
    title = 'I Love You'
    title2 = 'I Love you'
    upper = 'I LOVE YOU'
    upper2 = 'I LOVE You'
    lower = 'i love you'
    lower2 = 'I love you'
    print(space.isspace())  # True
    print(a.isspace())  # False
    print(title.istitle())  # True
    print(title2.istitle())  # False
    print(upper.isupper())  # True
    print(upper2.isupper())  # False
    print(lower.islower())  # True
    print(lower2.islower())  # False

# coding:utf-8

if __name__ == '__main__':

    a = 'abcdefg' 

print(a[::])  # abcdefg
    print(a[0:len(a):1])  # abcdefg

    print(a[::-1])  # gfedcba

  print(a[-2:-1:1])  # f