[Python]编程之美，,Task 1 : 首

[Python]编程之美，,Task 1 : 首

Task 1 : 首字母大写

import re     #python 正则表达式包：res=‘hello world‘s=re.sub(r"\w+",lambda match:match.group(0).capitalize(),s)

赏析：

re.sub，实现正则的替换。

re.sub(pattern, repl, string, count=0, flags=0)Return the string obtained by replacing the leftmost non-overlapping occurrences of pattern in string by the replacement repl. If the pattern isn’t found, string is returned unchanged. repl can be a string or a function; if it is a string, any backslash escapes in it are processed. That is, \n is converted to a single newline character, \r is converted to a carriage return, and so forth. Unknown escapes such as \j are left alone. Backreferences, such as \6, are replaced with the substring matched by group 6 in the pattern. For example:>>>>>> re.sub(r‘def\s+([a-zA-Z_][a-zA-Z_0-9]*)\s*\(\s*\):‘,...        r‘static PyObject*\npy_\1(void)\n{‘,...        ‘def myfunc():‘)‘static PyObject*\npy_myfunc(void)\n{‘If repl is a function, it is called for every non-overlapping occurrence of pattern. The function takes a single match object argument, and returns the replacement string. For example:>>>>>> def dashrepl(matchobj):...     if matchobj.group(0) == ‘-‘: return ‘ ‘...     else: return ‘-‘>>> re.sub(‘-{1,2}‘, dashrepl, ‘pro----gram-files‘)‘pro--gram files‘>>> re.sub(r‘\sAND\s‘, ‘ & ‘, ‘Baked Beans And Spam‘, flags=re.IGNORECASE)‘Baked Beans & Spam‘The pattern may be a string or an RE object.The optional argument count is the maximum number of pattern occurrences to be replaced; count must be a non-negative integer. If omitted or zero, all occurrences will be replaced. Empty matches for the pattern are replaced only when not adjacent to a previous match, so sub(‘x*‘, ‘-‘, ‘abc‘) returns ‘-a-b-c-‘.In string-type repl arguments, in addition to the character escapes and backreferences described above, \g<name> will use the substring matched by the group named name, as defined by the (?P<name>...) syntax. \g<number> uses the corresponding group number; \g<2> is therefore equivalent to \2, but isn’t ambiguous in a replacement such as \g<2>0. \20 would be interpreted as a reference to group 20, not a reference to group 2 followed by the literal character ‘0‘. The backreference \g<0> substitutes in the entire substring matched by the RE.Changed in version 2.7: Added the optional flags argument.

Pattern : r"w+"表示匹配数字和字母下划线的多个字符。

repl :lambda match:match.group(0).capitalize()表示首字母大写。

[Python]编程之美