定義
字符串是一個有序的字符的集合央串，用于存儲和表示基本的文本信息蚂踊，' '或'' ''或''' '''中間包含的內(nèi)容稱之為字符串
創(chuàng)建：
s = 'Hello,Eva约谈！How are you?'
特性：
按照從左到右的順序定義字符集合，下標從0開始順序訪問犁钟，有序
可以進行切片操作
不可變棱诱，字符串是不可變的，不能像列表一樣修改其中某個元素涝动，所有對字符串的修改操作其實都是相當(dāng)于生成了一份新數(shù)據(jù)迈勋。
補充：
1.字符串的單引號和雙引號都無法取消特殊字符的含義，如果想讓引號內(nèi)所有字符均取消特殊意義醋粟，在引號前面加r靡菇，如name＝r'l\thf'
字符串的常用操作
字符串操作方法有非常多，但有些不常用 米愿，我們只講重要的一些給大家厦凤，其它100年都用不上的有興趣可以自己研究
def capitalize(self):?
? ? 首字母大寫
def casefold(self):?
? ? 把字符串全變小寫
? ? >> > c = 'Alex Li'
? ? >> > c.casefold()
? ? 'alex li'
def center(self, width, fillchar=None):?
? ? >> > c.center(50, "-")
? ? '---------------------Alex Li----------------------'
def count(self, sub, start=None, end=None):?
? ? """
? ? S.count(sub[, start[, end]]) -> int
? ? >>> s = "welcome to apeland"
? ? >>> s.count('e')
? ? 3
? ? >>> s.count('e',3)
? ? 2
? ? >>> s.count('e',3,-1)
? ? 2
def encode(self, encoding='utf-8', errors='strict'):?
? ? """
? ? 編碼，日后講
def endswith(self, suffix, start=None, end=None):
? ? >> > s = "welcome to apeland"
? ? >> > s.endswith("land") 判斷以什么結(jié)尾
? ? True
def find(self, sub, start=None, end=None):?
? ? """
? ? S.find(sub[, start[, end]]) -> int
? ? Return the lowest index in S where substring sub is found,
? ? such that sub is contained within S[start:end].? Optional
? ? arguments start and end are interpreted as in slice notation.
? ? Return -1 on failure.
? ? """
? ? return 0
def format(self, *args, **kwargs):? # known special case of str.format
? ? >> > s = "Welcome {0} to Apeland,you are No.{1} user."
? ? >> > s.format("Eva", 9999)
? ? 'Welcome Eva to Apeland,you are No.9999 user.'
? ? >> > s1 = "Welcome {name} to Apeland,you are No.{user_num} user."
? ? >> > s1.format(name="Alex", user_num=999)
? ? 'Welcome Alex to Apeland,you are No.999 user.'
def format_map(self, mapping):?
? ? """
? ? S.format_map(mapping) -> str
? ? Return a formatted version of S, using substitutions from mapping.
? ? The substitutions are identified by braces ('{' and '}').
? ? """
? ? 講完dict再講這個
def index(self, sub, start=None, end=None):?
? ? """
? ? S.index(sub[, start[, end]]) -> int
? ? Return the lowest index in S where substring sub is found,
? ? such that sub is contained within S[start:end].? Optional
? ? arguments start and end are interpreted as in slice notation.
? ? Raises ValueError when the substring is not found.
? ? """
def isdigit(self):?
? ? """
? ? S.isdigit() -> bool
? ? Return True if all characters in S are digits
? ? and there is at least one character in S, False otherwise.
? ? """
? ? return False
def islower(self):?
? ? """
? ? S.islower() -> bool
? ? Return True if all cased characters in S are lowercase and there is
? ? at least one cased character in S, False otherwise.
? ? """
def isspace(self):?
? ? """
? ? S.isspace() -> bool
? ? Return True if all characters in S are whitespace
? ? and there is at least one character in S, False otherwise.
? ? """
def isupper(self):?
? ? """
? ? S.isupper() -> bool
? ? Return True if all cased characters in S are uppercase and there is
? ? at least one cased character in S, False otherwise.
? ? """
def join(self, iterable):?
? ? """
? ? S.join(iterable) -> str
? ? Return a string which is the concatenation of the strings in the
? ? iterable.? The separator between elements is S.
? ? """
? ? >>> n = ['alex','jack','rain']
? ? >>> '|'.join(n)
? ? 'alex|jack|rain'
def ljust(self, width, fillchar=None):?
? ? """
? ? S.ljust(width[, fillchar]) -> str
? ? Return S left-justified in a Unicode string of length width. Padding is
? ? done using the specified fill character (default is a space).
? ? """
? ? return ""
def lower(self):?
? ? """
? ? S.lower() -> str
? ? Return a copy of the string S converted to lowercase.
? ? """
? ? return ""
def lstrip(self, chars=None):?
? ? """
? ? S.lstrip([chars]) -> str
? ? Return a copy of the string S with leading whitespace removed.
? ? If chars is given and not None, remove characters in chars instead.
? ? """
? ? return ""
def replace(self, old, new, count=None):?
? ? """
? ? S.replace(old, new[, count]) -> str
? ? Return a copy of S with all occurrences of substring
? ? old replaced by new.? If the optional argument count is
? ? given, only the first count occurrences are replaced.
? ? """
? ? return ""
def rjust(self, width, fillchar=None):?
? ? """
? ? S.rjust(width[, fillchar]) -> str
? ? Return S right-justified in a string of length width. Padding is
? ? done using the specified fill character (default is a space).
? ? """
? ? return ""
def rsplit(self, sep=None, maxsplit=-1):?
? ? """
? ? S.rsplit(sep=None, maxsplit=-1) -> list of strings
? ? Return a list of the words in S, using sep as the
? ? delimiter string, starting at the end of the string and
? ? working to the front.? If maxsplit is given, at most maxsplit
? ? splits are done. If sep is not specified, any whitespace string
? ? is a separator.
? ? """
? ? return []
def rstrip(self, chars=None):?
? ? """
? ? S.rstrip([chars]) -> str
? ? Return a copy of the string S with trailing whitespace removed.
? ? If chars is given and not None, remove characters in chars instead.
? ? """
? ? return ""
def split(self, sep=None, maxsplit=-1):?
? ? """
? ? S.split(sep=None, maxsplit=-1) -> list of strings
? ? Return a list of the words in S, using sep as the
? ? delimiter string.? If maxsplit is given, at most maxsplit
? ? splits are done. If sep is not specified or is None, any
? ? whitespace string is a separator and empty strings are
? ? removed from the result.
? ? """
? ? return []
def startswith(self, prefix, start=None, end=None):?
? ? """
? ? S.startswith(prefix[, start[, end]]) -> bool
? ? Return True if S starts with the specified prefix, False otherwise.
? ? With optional start, test S beginning at that position.
? ? With optional end, stop comparing S at that position.
? ? prefix can also be a tuple of strings to try.
? ? """
? ? return False
def strip(self, chars=None):?
? ? """
? ? S.strip([chars]) -> str
? ? Return a copy of the string S with leading and trailing
? ? whitespace removed.
? ? If chars is given and not None, remove characters in chars instead.
? ? """
? ? return ""
def swapcase(self):?
? ? """
? ? S.swapcase() -> str
? ? Return a copy of S with uppercase characters converted to lowercase
? ? and vice versa.
? ? """
? ? return ""
def upper(self):?
? ? """
? ? S.upper() -> str
? ? Return a copy of S converted to uppercase.
? ? """
? ? return ""
def zfill(self, width):?
? ? """
? ? S.zfill(width) -> str
? ? Pad a numeric string S with zeros on the left, to fill a field
? ? of the specified width. The string S is never truncated.
? ? """
? ? return ""
