python 字符串创建，遍历，切片，格式化ljust rjust center,find,replace,split,repr,str

s = "abcdef"

遍历字符串

for i in [None] + range(-1,-len(s),-1):  每次比上一次上一个字符
print s[:i]

abcdef
abcde
abcd
abc
ab
a

print s[2:-1]

字符串对齐

print s.center(50,'*')    字符占宽度50,中间对齐，用*填充
print s.ljust(50,'-')     字符占宽度50，左对齐，用-填充
print s.rjust(50,'%')     字符占宽度50，右对齐，用%填充

**********************abcdef**********************
abcdef--------------------------------------------
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%abcdef

字符串操作

s1 += s2
s1 > s2
s1 == s2

字符与ascii 之间的转化

chr(65) ascii为65的字符
ord('a') 字符a的ascii

格式化输出

%s 转换成字符串
%d 十进制整数
%.2f 小数点后面2位
%x 16进制
% 字典输出
d = {'name':'xiaoming','age':16}
print '%(name)s  %(age)s'%(d)

str的帮助 (help(str)

>>> help(str)
Help on class str in module __builtin__:

class str(basestring)
|  str(object) -> string
|
|  Return a nice string representation of the object.
|  If the argument is a string, the return value is the same object.
|
|  Method resolution order:
|      str
|      basestring
|      object
|
|  Methods defined here:
|
|  __add__(...)
|      x.__add__(y) <==> x+y

>>> a = "hello"
>>> b = "world"
>>> a + b
'helloworld'
>>>

|

|  __contains__(...)
|      x.__contains__(y) <==> y in x
c = a + b
a in c  ==>True
|
|  __eq__(...)
|      x.__eq__(y) <==> x==y
|
a = "hello"
>>> b = "hello"
a == b  ==>True

|  __format__(...)
|      S.__format__(format_spec) -> string
|
|      Return a formatted version of S as described by format_spec.
|
|  __ge__(...)
|      x.__ge__(y) <==> x>=y
|  a = "hello"
>>> b = "world"
a > b ==>False

|  __getattribute__(...)
|      x.__getattribute__('name') <==> x.name
|
|  __getitem__(...)
|      x.__getitem__(y) <==> x[y]
|
|  __getnewargs__(...)
|
|  __getslice__(...)
|      x.__getslice__(i, j) <==> x[i:j]
|
|      Use of negative indices is not supported.
|  a[1:3] ⇒ 'el'
|  __gt__(...)
|      x.__gt__(y) <==> x>y
|  a > b ==>False

|  __hash__(...)
|      x.__hash__() <==> hash(x)
|
|  __le__(...)
|      x.__le__(y) <==> x<=y
|  a <= b ==>True
|  __len__(...)
|      x.__len__() <==> len(x)
|  len(a)  ⇒ 5
|  __lt__(...)
|      x.__lt__(y) <==> x<y
|  a < b ==>True
|  __mod__(...)
|      x.__mod__(y) <==> x%y
|
|  __mul__(...)
|      x.__mul__(n) <==> x*n
|a * 5
'hellohellohellohellohello'

|  __ne__(...)
|      x.__ne__(y) <==> x!=y
|  a != b
True
|  __repr__(...)
|      x.__repr__() <==> repr(x)
|  repr(a)
"'hello'"
|  __rmod__(...)
|      x.__rmod__(y) <==> y%x
|
|  __rmul__(...)
|      x.__rmul__(n) <==> n*x
|
|  __sizeof__(...)
|      S.__sizeof__() -> size of S in memory, in bytes
|
|  __str__(...)
|      x.__str__() <==> str(x)
|  str(a)
'hello'
|  capitalize(...)
|      S.capitalize() -> string
|a.capitalize()
'Hello'
|      Return a copy of the string S with only its first character
|      capitalized.
|
|  center(...)
|      S.center(width[, fillchar]) -> string
|  a.center(50,'*')
'**********************hello***********************'
|      Return S centered in a string of length width. Padding is
|      done using the specified fill character (default is a space)
|
|  count(...)
|      S.count(sub[, start[, end]]) -> int
|
|      Return the number of non-overlapping occurrences of substring sub in
|      string S[start:end].  Optional arguments start and end are interpreted
|      as in slice notation.
a= "helloho"
|  a.count('h')
2
|  decode(...)
|      S.decode([encoding[,errors]]) -> object
|
|      Decodes S using the codec registered for encoding. encoding defaults
|      to the default encoding. errors may be given to set a different error
|      handling scheme. Default is 'strict' meaning that encoding errors raise
|      a UnicodeDecodeError. Other possible values are 'ignore' and 'replace'
|      as well as any other name registered with codecs.register_error that is
|      able to handle UnicodeDecodeErrors.
|
|  encode(...)
|      S.encode([encoding[,errors]]) -> object
|
|      Encodes S using the codec registered for encoding. encoding defaults
|      to the default encoding. errors may be given to set a different error
|      handling scheme. Default is 'strict' meaning that encoding errors raise
|      a UnicodeEncodeError. Other possible values are 'ignore', 'replace' and
|      'xmlcharrefreplace' as well as any other name registered with
|      codecs.register_error that is able to handle UnicodeEncodeErrors.
|
|  endswith(...)
|      S.endswith(suffix[, start[, end]]) -> bool
|
|      Return True if S ends with the specified suffix, False otherwise.
|      With optional start, test S beginning at that position.
|      With optional end, stop comparing S at that position.
|      suffix can also be a tuple of strings to try.
e6de

a.endswith("ho") ==>True |

|  expandtabs(...)
|      S.expandtabs([tabsize]) -> string
|
|      Return a copy of S where all tab characters are expanded using spaces.
|      If tabsize is not given, a tab size of 8 characters is assumed.
|
|  find(...)
a.find("ho")
5
|      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.
|
|  format(...)
|      S.format(*args, **kwargs) -> string
|
|      Return a formatted version of S, using substitutions from args and kwargs.
|      The substitutions are identified by braces ('{' and '}').
|
|  index(...)
|      S.index(sub [,start [,end]]) -> int
|
|      Like S.find() but raise ValueError when the substring is not found.
a.index("h")
0
|

|  isalnum(...)
|      S.isalnum() -> bool
|
|      Return True if all characters in S are alphanumeric
|      and there is at least one character in S, False otherwise.
|  a = "99hhhhxx\t"
>>> a.isalnum()
False
|  isalpha(...)
|      S.isalpha() -> bool
|
|      Return True if all characters in S are alphabetic
|      and there is at least one character in S, False otherwise.
|
|  isdigit(...)
|      S.isdigit() -> bool
|
|      Return True if all characters in S are digits
|      and there is at least one character in S, False otherwise.
|  a = "0123456789"
>>> a.isdigit()
True
|  islower(...)
|      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.
|  a = "aaaaa13455"
>>> a.islower()
True
|  isspace(...)
|      S.isspace() -> bool
|
|      Return True if all characters in S are whitespace
|      and there is at least one character in S, False otherwise.
|  a.isspace()
False
|  istitle(...)
|      S.istitle() -> bool
|  a.title()
'Aaaaa13455'
a.istitle()
|      Return True if S is a titlecased string and there is at least one
|      character in S, i.e. uppercase characters may only follow uncased
|      characters and lowercase characters only cased ones. Return False
|      otherwise.
|
|  isupper(...)
|      S.isupper() -> bool
|   a.isupper() False
|      Return True if all cased characters in S are uppercase and there is
|      at least one cased character in S, False otherwise.
|
|  join(...)
|      S.join(iterable) -> string
|
|      Return a string which is the concatenation of the strings in the
|      iterable.  The separator between elements is S.
|
c = ["aa","bb","cc"]
>>> ','.join(c)
'aa,bb,cc'
|  ljust(...)
|      S.ljust(width[, fillchar]) -> string
|
|      Return S left-justified in a string of length width. Padding is
|      done using the specified fill character (default is a space).
|  a.ljust(100,'*')
'hello,world*****************************************************************************************'
|  lower(...)
|      S.lower() -> string
|
|      Return a copy of the string S converted to lowercase.
|  a = string.uppercase
>>> a
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> a.lower()
'abcdefghijklmnopqrstuvwxyz'
>>>

|  lstrip(...)
|      S.lstrip([chars]) -> string or unicode
|
|      Return a copy of the string S with leading whitespace removed.
|      If chars is given and not None, remove characters in chars instead.
|      If chars is unicode, S will be converted to unicode before stripping

a = "      hello world    "
>>> a.lstrip()
'hello world    '
>>>

|

|  partition(...)
|      S.partition(sep) -> (head, sep, tail)
|
|      Search for the separator sep in S, and return the part before it,
|      the separator itself, and the part after it.  If the separator is not
|      found, return S and two empty strings.
|
|  replace(...)
|      S.replace(old, new[, count]) -> string
|
|      Return a copy of string S with all occurrences of substring
|      old replaced by new.  If the optional argument count is
|      given, only the first count occurrences are replaced.
a = "abcde"
>>> a.replace('c','H***H')
'abH***Hde'
>>>
|
|  rfind(...)
|      S.rfind(sub [,start [,end]]) -> int
|
|      Return the highest 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.

>>> a = "abcdea"
>>> a.find('a')
0
>>> a.rfind('a')
5

|

|  rindex(...)
|      S.rindex(sub [,start [,end]]) -> int
|
|      Like S.rfind() but raise ValueError when the substring is not found.

>>> a.index('a')
0
>>> a.rindex('a')
5
>>>

|

|  rjust(...)
|      S.rjust(width[, fillchar]) -> string
|
|      Return S right-justified in a string of length width. Padding is
|      done using the specified fill character (default is a space)

>>> a.rjust(100,"*")
'**********************************************************************************************abcdea'
>>>

|

|  rpartition(...)
|      S.rpartition(sep) -> (head, sep, tail)
|
|      Search for the separator sep in S, starting at the end of S, and return
|      the part before it, the separator itself, and the part after it.  If the
|      separator is not found, return two empty strings and S.
|
|  rsplit(...)
|      S.rsplit([sep [,maxsplit]]) -> list of strings
|
|      Return a list of the words in the string 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 or is None, any whitespace string
|      is a separator.

>>> str1 = "a,b,c,d,e,f,"
>>> str1.rsplit(',',1)
['a,b,c,d,e,f', '']
>>> |

|  rstrip(...)
|      S.rstrip([chars]) -> string or unicode
|
|      Return a copy of the string S with trailing whitespace removed.
|      If chars is given and not None, remove characters in chars instead.
|      If chars is unicode, S will be converted to unicode before stripping

>>> str1 = "     Helo,wollll    "
>>> str1.rstrip()
'     Helo,wollll'
>>>

|

|  split(...)
|      S.split([sep [,maxsplit]]) -> list of strings
|
|      Return a list of the words in the string 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.

>>> str1 = "a,b,c,d,e,f,"
>>> str1.split()
['a,b,c,d,e,f,']
>>>

|

|  splitlines(...)
|      S.splitlines([keepends]) -> list of strings
|
|      Return a list of the lines in S, breaking at line boundaries.
|      Line breaks are not included in the resulting list unless keepends
|      is given and true.
|
|  startswith(...)
|      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.

>>> str1.startswith("a")
True
>>>

|

|  strip(...)
|      S.strip([chars]) -> string or unicode
|
|      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.
|      If chars is unicode, S will be converted to unicode before stripping

>>> str1 = "     Helo,wollll    "
>>> str1.strip()
'Helo,wollll'
>>>

|

|  swapcase(...)
|      S.swapcase() -> string
|
|      Return a copy of the string S with uppercase characters
|      converted to lowercase and vice versa.

>>> str1 = "     Helo,wollll    "
>>> str1.strip()
'Helo,wollll'
>>>
>>>
>>> str1.swapcase()
'     hELO,WOLLLL    '
>>>

|

|  title(...)
|      S.title() -> string
|
|      Return a titlecased version of S, i.e. words start with uppercase
|      characters, all remaining cased characters have lowercase.
a = "hello,world"
>>> a.title()
'Hello,World'
>>>
|

|  translate(...)
|      S.translate(table [,deletechars]) -> string
|
|      Return a copy of the string S, where all characters occurring
|      in the optional argument deletechars are removed, and the
|      remaining characters have been mapped through the given
|      translation table, which must be a string of length 256 or None.
|      If the table argument is None, no translation is applied and
|      the operation simply removes the characters in deletechars.
|
|  upper(...)
|      S.upper() -> string
|
|      Return a copy of the string S converted to uppercase.

>>> str1.swapcase()
'     hELO,WOLLLL    '
>>> a = "hello,world"
>>> a.title()
'Hello,World'
>>> a.upper()
'HELLO,WORLD'
>>>

|

|  zfill(...)
|      S.zfill(width) -> string
|
|      Pad a numeric string S with zeros on the left, to fill a field
|      of the specified width.  The string S is never truncated.
|
|  ----------------------------------------------------------------------
|  Data and other attributes defined here:
|
|  __new__ = <built-in method __new__ of type object>
|      T.__new__(S, ...) -> a new object with type S, a subtype of T