>>> "www.jb51.net" #字符串使用单引号（'）或双引号（"）表示
'www.jb51.net'
>>> 'www.jb51.net'
'www.jb51.net'
>>> "www."+"jb51"+".net" #字符串可以用“+”号连接
'www.jb51.net'
>>> "#"*10 #字符串可以使用“*”来代表重复次数
'##########'
>>> "What's your name?" #单引号中可以直接使用双引号，同理双引号中也可以直接使用单引号
"What's your name?"
>>> path = r"C:\newfile" #此处r开头表示原始字符串，里面放置的内容都是原样输出
>>> print(path)
C:\newfile

>>> str1 = "python test"
>>> "test" in str1 #这里in用来判断元素是否在序列中
True
>>> len(str1) #这里len()函数求字符串长度
11
>>> max(str1)
'y'
>>> min(str1)
' '

>>> "I like %s" % "python" #使用%进行格式化输出的经典表示方式
'I like python'
>>> dir(str) #列出字符串所有属性与方法
['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'capitalize', 'casefold', 'center', 'count', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'format_map', 'index', 'isalnum', 'isalpha', 'isdecimal', 'isdigit', 'isidentifier', 'islower', 'isnumeric', 'isprintable', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'maketrans', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

>>> str = "I like {1} and {2}" #这里{1}表示占位符（注意：这里得从{0}开始）
>>> str.format("python","PHP")
Traceback (most recent call last):
 File "<pyshell#5>", line 1, in <module>
  str.format("python","PHP")
IndexError: tuple index out of range
>>> str = "I like {0} and {1}"
>>> str.format("python","PHP")
'I like python and PHP'
>>> "I like {1} and {0}".format("python","PHP")
'I like PHP and python'
>>> "I like {0:20} and {1:>20}".format("python","PHP")#{0:20}表示第一个位置占据20个字符，并且左对齐。{1:>20}表示第二个位置占据20个字符，且右对齐
'I like python        and         PHP'
>>> "I like {0:.2} and {1:^10.2}".format("python","PHP")#{0:.2}表示第一个位置截取2个字符，左对齐。{1:^10.2}表示第二个位置占据10个字符，且截取2个字符，^表示居中
'I like py and   PH  '
>>> "age: {0:4d} height: {1:6.2f}".format("32","178.55") #这里应该是数字，不能用引号，否则会被当作字符串而报错！
Traceback (most recent call last):
 File "<pyshell#0>", line 1, in <module>
  "age: {0:4d} height: {1:6.2f}".format("32","178.55")
ValueError: Unknown format code 'd' for object of type 'str'
>>> "age: {0:4d} height: {1:8.2f}".format(32,178.5523154) #这里4d表示长度为4个字符的整数，右对齐。8.2f表示长度为8，保留2位小数的浮点数，右对齐。
'age:  32 height:  178.55'

>>> "I like {str1} and {str2}".format(str1 = "python",str2 ="PHP")
'I like python and PHP'
>>> data = {"str1":"PHP","str2":"Python"}
>>> "I like {str1} and {str2}".format(**data)
'I like PHP and Python'

>>> # isalpha()判断字符串是否全部为字母
>>> str1 = "I like python" #这里str1里面有空格
>>> str1.isalpha()
False
>>> str2 = "pythonDemo" #这里为全部是字母
>>> str2.isalpha()
True

>>> # split()分割字符串
>>> smp = "I like Python"
>>> smp.split(" ")
['I', 'like', 'Python']

>>> # strip()去除字符串两端空格 ，类似的，lstrip去除左侧空格，rstrip去除右侧空格
>>> strDemo = "  python demo  "
>>> strDemo.strip() #类似于php中的trim()函数
'python demo'
>>> "****python**".strip("*") #strip()函数还可删除指定字符
'python'

>>> #字符串拼接（对于+不适用的情况下可以使用）
>>> smp = "I like Python"
>>> c = smp.split(" ")
>>> c = "I like python".split()
>>> type(c) #这里检测类型，可以看到c为列表
<class 'list'>
>>> "*".join(c)
'I*like*Python'
>>> " ".join(c)
'I like Python'
>>> " ".join(["I","Like","python"]) #这里可以直接使用列表作为join函数的参数
'I Like python'
>>> " ".join("abcd") #也可直接使用字符串作为join函数的参数
'a b c d'

>>> # count()函数统计指定字符串出现次数
>>> "like python,learn python".count("python")
2

>>> # find()函数查找指定字符串出现位置
>>> "python Demo".find("python")
0
>>> "python Demo".find("Demo")
7

>>> # replace(old,new)函数替换指定字符串(old)为新字符串(new)
>>> "I like php".replace("php","python")
'I like python'