"Python advanced" 02, Text Processing and IO in-depth understanding

1, there is a file, the word between the use of spaces, semicolons, commas, or periods separated, please extract all the words.

Solution:

use \w to match and extract words, but there is a miscarriage of judgment

Use Str.split to separate character strings, but multiple separators are required

Separating strings with Re.split

In [4]: "Help (Re.split)" Help "on Function" split in module Re:split (pattern, String, maxsplit=0, flags=0) split the source String by the occurrences of the pattern, returning a list containing the resulting substrings.

in [23]: text =  "I ' m xj, i love python,,linux;   i  don ' T like windows. " In [24]: fs = re.split (R "(, |\.|;| \s) +\s* ",  text) in [25]: fsout[25]: [" I ' M ",  '   ',  ' XJ ',  '   ',  ' I ',  '   ',  ' love ',  '   ',  ' Python ',  ', ',  ' Linux ',  '   ',  ' I ',   '   ',  "don ' t",  '   ',  ' like ',  '   ',  ' windows ',  '. ',  ']in  [26]: fs[::2]             #提取出单词Out [26]:  ["I ' M",  ' XJ ',  ' i ',  ' love ',  ' Python ',  ' Linux ',  ' i ',  "don ' t",  ' Like ',  ' windows ',  ']in [27]: fs[1::2]       #提取出符号Out [27]:  ['   ',  '   ',  '   ',  '   ',  ', ',  '   ',  '   ',  '   ',  '   ',  '. in [53]: fs = re.findall (r "[^,\.;\ s]+ ",  text) in [54]: fsout[54]: [" I ' M ",  ' XJ ',  ' i ',  ' love ',  ' Python ',   ' Linux ',  ' i ',  "don ' t",  ' like ',  ' windows ']in [55]: fh =  Re.findall (R ' [, \.;\ S] ',  text) in [56]: fhout[56]: ['   ',  ', ',  '   ',  '   ',  '   ',  ', ',  ', ',  '; ',  '   ',  '   ',  '   ',  '   ',  '. '

2, there is a directory, saved a number of files, find all of them C source files (. C and. h)

Solution:

Using Listdir

Use Str.endswith to judge

in [13]: s =  "XJ.C" In [14]: s.endswith (". C") out[14]: truein [15]:  s.endswith (". H") Out[15]: falsein [16]: import osin [17]: os.listdir ("/usr/ include/") out[17]: [' libmng.h ',  ' netipx ',  ' ft2build.h ',  ' ' FlexLexer.h ',  ' SELinux ',   ' qtsql ',  ' resolv.h ',  ' gio-unix-2.0 ',  ' wctype.h ' ",  ' python2.6 ',  ' ' scsi ',  .  . .  ' Qtopengl ',  ' mysql ',  ' byteswap.h ',,  ' xj.c '   ' mntent.h ',  ' Semaphore.h ',  ' stdio_ext.h ',  ' libxml2 '] in [21]: for filename in  Os.listdir ("/usr/include"):     if filename.endswith (". C"):         print filename   ....:          xj.cin [22]: for filename in os.listdir ("/usr/include"):     if filename.endswith (". C",   ". H ")):           #这里元祖是或的关系          print filename   ....:          libmng.hft2build.hflexlexer.hnss.hpng.hutime.hieee754.hfeatures.hxj.c...verto-module.hsemaphore.hstdio_ EXT.HIN [23]:

3. Fnmath Module

support for Shell-like wildcard characters

In [24]: help (Fnmatch)            # Case sensitivity is consistent with operating system Help on function fnmatch in module fnmatch:fnmatch (NAME, PAT)     Test whether FILENAME matches PATTERN.         Patterns are Unix shell style:         *       matches everything    ?        MATCHES ANY SINGLE CHARACTER    [SEQ]    matches any character in seq    [!seq]   matches any char not in seq        an  initial period in filename is not special.    both  filename and pattern are first case-normalized    if the operating system  Requires it.    if you don ' T want this, use fnmatchcase (Filename, pattern). ~ (END)  in [47]: fnmatch.fnmatch ("Sba.txt",  "*txt") out[47]:  Truein [48]: fnmatch.fnmatch ("Sba.txt",  "*t") out[48]: truein [49]:  Fnmatch.fnmatch ("Sba.txt",  "*b") Out[49]: falsein [50]: fnmatch.fnmatch ("Sba.txt",  "*b * ") out[50]: true

Case: you have a program that handles files, the file names are entered by the user, and you need to support the same wildcard characters as the shell.

[email protected] src]# cat test1.py #!/usr/local/bin/python2.7#coding:utf-8import osimport sysfrom fnmatch Import Fnma Tchret = [name for name in Os.listdir (sys.argv[1]) if Fnmatch (name, sys.argv[2])]print ret[[email protected] src]# Python2 .7 test1.py/usr/include/*.c[' XJ.C ']

4, Re.sub () text Substitution

in [53]: help (re.sub) help on function sub  In module re:sub (pattern, repl, string, count=0, flags=0)      Return the string obtained by replacing the leftmost     non-overlapping occurrences of the pattern in string by  the    replacement repl.  repl can be either a  String or a callable;    if a string, backslash escapes  in it are processed.  if it is    a callable ,  it ' s passed the match object and must return     a replacement string to be used. 

Case: There is a text, the date in the text using the%m/%d/%y format, you need to convert it all to%y-%m-%d format.

in [+]: Text = "Today is 11/08/2016, next class time 11/15/2016" in []: New_text = re.sub (R ' (\d+)/(\d+)/(\d+) ', R ' \3-\2- \1 ', text) in [the]: new_textout[57]: ' Today is 2016-08-11, next class time 2016-15-11 '

5, Str.format string Formatting

Case: You need to create a small template engine that does not require logical control, but needs to use variables to populate the template

in [[+]: Help (Str.format) Help on Method_descriptor:format (...)    S.format (*args, **kwargs), string Return A formatted version of S, using substitutions from args and Kwargs. The substitutions is identified by braces (' {' and '} '). (END)

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"Python advanced" 02, Text Processing and IO in-depth understanding