getline3

The getline3 module for Python3 provides a simple interface to read a line from an input stream and pass it to the specified function. An input stream can be a regular file, stdin, or pipe.

Bonus: This module has the functions that print out a string to stderr.

• getline3.eprint(*args, **kwargs)
• fetline3.ewrite(string)

You can use them like as follows:

  import getline3
  getline = getline3.getline
  eprint = getline3.eprint
  ewrite = getline3.ewrite

  eprint('ERROR:')

eprint() adds a newline to the end the string while ewrite() does not.

Usage

#!/usr/bin/env python3
import getline3
import re

#
# for convenience
#
getline = getline3.getline
eprint = getline3.eprint
ewrite = getline3.ewrite

def main():
    #
    # 1. Instantiate getline object.
    #    The parameter specifies an input stream
    #
    f = getline('/etc/passwd') # regular file
    s = getline('-')           # stdin
    p = getline('ls /etc |')   # pipe

    #
    # 2.1. Get the file descriptor associated with the input stream 
    #
    fd = p.fd()

    #
    # 2.2. runLoop() reads input stream line by line:
    #      param 1:  function to be called each time a new line is read
    #                (processLine() in this example)
    #      param 2:  True:  line is stripped
    #                False: line is *NOT* stripped
    #      param 3-: all parameters from the 3rd are passed to processLine()
    #
    #      Return value:
    #       True:  input stream reached EOF (end of file)
    #       False: runLoop() exited before the input stream reached EOF
    #
    rc = p.runLoop(processLine, False, 0)
    if rc == True:
        print('*** Reached the end of file ***')
    else:
        print('*** Quit before reaching the end of file ***')

    #
    # 3. destruct the getline object
    #
    del p
    del f
    del s


#
# processLine():
#  param 1:  pointer to the getline object
#  param 2:  line to be processed
#  param 3-: passed from p.runLoop()
#
#  Return value:
#    True:  p.runLoop() to continue to read lines
#    False: p.runLoop() to stop reading lines and return False
#
def processLine(p, line, *argv):
    r = re.compile(r'^(.*).conf$')
    line = p.chop(line)
    m = r.search(line)
    if m != None:
        print(m.group(1))

    return True

if __name__ == '__main__':
    main()

How to test the module

  python -m unittest -v getline