Python shlex class














































Python shlex class



                                                               Python Shlex class
Hello,This is Rohit Kumar.In this article I will talk about shlex class in the shlex module. 
The shlex module defines the following class:
class shlex.shlex(instream=None, infile=None, posix=False, punctuation_chars=False)

We Know that  a shlex instance or subclass instance is a lexical analyzer object. The initialization argument, if present, specifies where to read characters from. It must be a file-/stream-like object with read() and readline() methods, or a string. If no argument is given, input will be taken from sys.stdin. The second optional argument is a filename string, which sets the initial value of the infile attribute. If the instream argument is omitted or equal to sys.stdin, this second argument defaults to "stdin". The posix argument defines the operational mode: when posix is not true (default), the shlex instance will operate in compatibility mode. When operating in POSIX mode, shlex will try to be as close as possible to the POSIX shell parsing rules. The punctuation_chars argument provides a way to make the behaviour even closer to how real shells parse. This can take a number of values: the default value, False, preserves the behaviour seen under Python 3.5 and earlier. If set to True, then parsing of the characters ();<>|& is changed: any run of these characters (considered punctuation characters) is returned as a single token. If set to a non-empty string of characters, those characters will be used as the punctuation characters. Any characters in the wordchars attribute that appear in punctuation_chars will be removed from wordchars. See Improved Compatibility with Shells for more information. punctuation_chars can be set only upon shlex instance creation and can not be modified later.
                                                       Configparser vs Shlex Module
Configparser:
This module provides the ConfigParser class which implements a basic configuration language which provides a structure similar to what's found in Microsoft Windows INI files. You can use this to write Python programs which can be customized by end users easily.
Shlex:
Support for a creating Unix shell-like mini-languages which can be used as an alternate format for application configuration files.
                                                                       Using shlex class
import shlex
lexer = shlex.shlex(open("samples/sample.netrc", "r"))
lexer.wordchars = lexer.wordchars + "._"

while 1:
    token = lexer.get_token()
    if not token:
        break
    print(repr(token))

Result:
'machine'
'secret.fbi'
'login'
'mulder'
'password'
'trustno1'
'machine'
'non.secret.fbi'
'login'
'scully'
'password'
'noway




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