Python字符串常用方法以及其应用场景详解

>>> choice = input('是否继续执行程序，输入n或N则结束：')
是否继续执行程序，输入n或N则结束：N
>>> if choice == 'n'or choice == 'N':  # 常规处理方式
	      print('程序结束')
>>> if choice.lower() == 'n':  #  推荐用该方法处理
	      print('程序结束')

>>> words = ['When', 'you', 'fall', 'stand', 'up.', 'And', 'when', 'you', 'break', 'stand', 'tough', 'And', 'when', 'they', 'say', 'you', 'can't,', 'you', 'say', 'I', 'can', 'I', 'can']
>>> count = 0
>>> sta_word = 'when'
>>> for word in words:
	    if word.lower() == sta_word:
		    count  = 1
>>> print('{}出现了{}次'.format('when', count))
when出现了3次

>>> "帽子和服装如何搭配才好看".count("和服")
1
>>> import jieba
>>> words = jieba.lcut("帽子和服装如何搭配才好看")
>>> words
['帽子','和','服装','如何','搭配','才','好看']
>>> words.count("和服") # 分词后再统计
0

>>> temp_str = "  tomorrow is another day "
>>> temp_str.strip()
'tomorrow is another day'
>>> temp_str = "#  tomorrow is another day @"
>>> temp_str.strip('#')
'  tomorrow is another day @'
>>> temp_str.strip('# @')
'tomorrow is another day'
>>> temp_str = "#@  tomorrow is another day @"
>>> temp_str.lstrip('@# ')
'tomorrow is another day @'

>>> temp_str = "Whatever is worth doing is worth doing well"
>>> temp_str.split()
['Whatever', 'is', 'worth', 'doing', 'is', 'worth', 'doing', 'well']
>>> temp_str = "tomorrow#is#another#day"
>>> temp_str.split('#')
['tomorrow', 'is', 'another', 'day']
>>> temp_str = ‘"name":"Mike","age":18,"sex":"male","hair":"black"'
>>> temp_str.split(',')
['"name":"Mike"', '"age":18', '"sex":"male"', '"hair":"black"']

>>> temp_str = "this is really interesting, and that is boring."
>>> temp_str.replace('is','was')
'thwas was really interesting, and that was boring.'
>>> temp_str.replace('is','was')
'this was really interesting, and that was boring.'
>>> temp_str = 'I really really really like you.'
>>> temp_str.replace("really","",2)
'I   really like you.'

>>> seq = 'hello world'
>>> ":".join(seq)
'h:e:l:l:o: :w:o:r:l:d'
>>> seq = ('Whatever', 'is', 'worth', 'doing', 'is', 'worth', 'doing', 'well')
>>> "*".join(seq)
'Whatever*is*worth*doing*is*worth*doing*well'
>>> seq = ['Whatever', 'is', 'worth', 'doing', 'is', 'worth', 'doing', 'well']
>>> " ".join(seq)
'Whatever is worth doing is worth doing well'
>>> seq = ['"name":"Mike"', '"age":18', '"sex":"male"', '"hair":"black"']
>>> "#".join(seq)
'"name":"Mike"#"age":18#"sex":"male"#"hair":"black"'

>>> num = "13579"
>>> num.isdigit()
True
>>> num = '1.0'
>>> num.isdigit()
False
>>> num = '-1'
>>> num.isdigit()
False

>>> t = ''
>>> t.isspace()
False
>>> t = '  '
>>> t.isspace()
True

>>> temp_str = "Whatever is worth doing is worth doing well"
>>> temp_str.startswith("W")
True
>>> temp_str.startswith("What")
True
>>> temp_str.startswith('Whatever',2)
False
>>> temp_str.endswith("well",2)
True
>>> temp_str.endswith("we",2,-2)
True

a = "hello world"
# 字符串不能通过索引进行修改  name[0] = 'q'
 
# 切片，查找字符串当中的一段值，[起始值:终止值:步长]不写步长默认是1
print(a[0:5:])
print(a[::-1])  # 步长负数倒过来走，不写起始值和终止值就走完全部
print(a[::1])
print(len(a))  # len方法获取字符串的长度
 
# in 和 not in :判断一个字符串是否在一个大的字符串中
# 返回值为布尔类型
print('hello' in 'hello world')
print('nihao' not in 'hello world')
 
# 字符串的增
print('nihao', 'Python')
print('nihao'   'Python')
 
# format    前面的大括号写上数字代表着取后面括号里的索引位置
print('==============format================')
print('my name is {}'.format(100))
print('my name is {1},my age is {0}'.format('dayv', 18))
print('my name is {0},my age is {1}'.format('dayv', 18))
 
# join  把列表里的元素组成字符串
str1 = '真正的勇士'
str2 = '敢于直面惨淡的人生'
str3 = '敢于正视淋漓的鲜血'
print(''.join([str1, str2, str3]))
# 前面的逗号表示用什么来隔开，列表中只能是字符串才能使用join方法
print('，'.join([str1, str2, str3]))
 
# 删   del
name1 = 'nihao'
del name1  # 这就把这个变量删除了，在输出这个变量就会出错
 
# 改
# 字符串变大小写 upper , lower ,
name1 = 'abc'
print('大写：'   name1.upper())
print(name1.lower())
 
# capitalize  将第一个字母转换成大写
print(name1.capitalize())
 
# 将每个单词的首字母大写  title
name2 = 'hello world'
print('每个单词首字母大写：'   name2.title())
print('原name2的值'   name2)
 
# 将字符串切分成列表  默认空格为字符切分  split
name1 = 'a b    cd e'
print(name1.split())
# 括号里写什么就用什么切分                !!!!!!!!!!!!!!!!!!!!
name1 = 'a1b1cd1e'
print("自己配置用什么东西切分", name1.split('1'))  # 返回的是列表
# rsplit('指定用什么切片', 切几次),反过来切
print('切片倒过来切使用rsplit', name1.rsplit('1', 1))  # 倒过来切一个元素
# 替换replace(被替换的字符,替换的字符，个数)     !!!!!!!!!!!!!!
print(name1.replace('1', '0'))
print(name1.replace('1', '0', 1))  # 个数是从左往右的顺序替换
aaaaa = ' sdf   kkf  k k   '
print('使用替换去除字符串中的全部空格', aaaaa.replace(" ", ''))
 
# strip  除去字符串两边的空格，中间的不会管
name1 = '        ni h ao     '
print(name1.strip())
 
# 查
# find  index
# 查找字符串在大字符串的那个索引位置（起始索引）
name1 = 'PythonPythonPython'
print("使用find查找的索引位置", name1.find('on'))
# 找不到会返回-1
print("使用index查找的索引位置：", name1.index('on'))
# index方法找不到会报错
 
# count  统计一个字符串在大字符串里面出现的次数
print(name1.count('qi'))
 
# 判断一个字符串里的数据是不是都是数字  isdigit   返回布尔值
num = '156465'
print(num.isdigit())
# 判断一个字符串里的数据是不是都是字母   isalpha
num = 'ksdjflks'
print(num.isalpha())
 
# 比较后面一个元素是否是前面一个元素的开头，startswith
# 比较后面一个元素是否是前面一个元素的结尾  endswith
mm = 'Python nihao'
print(mm.startswith('Pyth'))
print(mm.endswith('Pytho'))
 
# 判断字符串是否全是大写isupper   是否全是小写islower
 
# 转义字符 \n换行   \t
print('hello \nworld')
print('z\tiyu')
print('Pyth \t on')
print('Python123')
# 反转义
print(r'zhai \t dada')  # 加r
print('zhai \\t dada')  # 或者写两个斜杠
 
# 控制字符串的输入字数
print('123456'[:5])  # 只会输入前五个数