├── README.md
└── cat.py


/README.md:
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1 | # IllustratedPy3
2 | 
3 | If you have questions or concerns, click on Issues above. Please search if there is a similar issue. If not, please file an issue.
4 | 


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/cat.py:
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  1 | #!/usr/bin/env python3
  2 | 
  3 | r"""A simple implementation of the unix ``cat``
  4 | command. It only implements the ``--number``
  5 | option. It is useful for illustrating file
  6 | layout and best practices in Python.
  7 | 
  8 | This is a triple quoted docstring for the whole
  9 | module (this file). If you import this module
 10 | somewhere else and run ``help(cat)``, you will
 11 | see this.
 12 | 
 13 | This docstring also contains a ``doctest`` which
 14 | serves as an example of programmatically using
 15 | the code. It also functions as a doctest. The
 16 | ``doctest`` module can execute this docstring
 17 | and validate it by checking any output.
 18 | 
 19 | >>> import io
 20 | >>> fin = io.StringIO(\
 21 | ...     'hello\nworld\n')
 22 | >>> fout = io.StringIO()
 23 | >>> cat = Catter([fin],
 24 | ...     show_numbers=True)
 25 | >>> cat.run(fout)
 26 | >>> print(fout.getvalue())
 27 |      1  hello
 28 |      2  world
 29 | <BLANKLINE>
 30 | """
 31 | 
 32 | import argparse
 33 | import logging
 34 | import sys
 35 | 
 36 | 
 37 | __version__ = '0.0.1'
 38 | 
 39 | 
 40 | logging.basicConfig(
 41 |     level=logging.DEBUG)
 42 | 
 43 | 
 44 | class Catter(object):
 45 |     """
 46 |     A class to concatenate files to
 47 |     standard out
 48 | 
 49 |     This is a class docstring,
 50 |     ``help(cat.Catter)`` would show
 51 |     this.
 52 |     """
 53 | 
 54 |     def __init__(self, files,
 55 |                  show_numbers=False):
 56 |         self.files = files
 57 |         self.show_numbers = show_numbers
 58 | 
 59 |     def run(self, fout):
 60 |         # use 6 spaces for numbers and right align
 61 |         fmt = '{0:>6}  {1}'
 62 |         count = 1
 63 |         for fin in self.files:
 64 |             logging.debug('catting {0}'.format(fin))
 65 |             for line in fin.readlines():
 66 |                 if self.show_numbers:
 67 |                     fout.write(fmt.format(
 68 |                         count, line))
 69 |                     count += 1
 70 |                 else:
 71 |                     fout.write(line)
 72 | 
 73 | 
 74 | def main(args):
 75 |     """
 76 |     Logic to run a cat with arguments
 77 |     """
 78 |     parser = argparse.ArgumentParser(
 79 |         description='Concatenate FILE(s), or '
 80 |         'standard input, to standard output')
 81 |     parser.add_argument('--version',
 82 |         action='version', version=__version__)
 83 |     parser.add_argument('-n', '--number',
 84 |         action='store_true',
 85 |         help='number all output lines')
 86 |     parser.add_argument('files', nargs='*',
 87 |         type=argparse.FileType('r'),
 88 |         default=[sys.stdin], metavar='FILE')
 89 |     parser.add_argument('--run-tests',
 90 |         action='store_true',
 91 |         help='run module tests')
 92 |     args = parser.parse_args(args)
 93 | 
 94 |     if args.run_tests:
 95 |         import doctest
 96 |         doctest.testmod()
 97 |     else:
 98 |         cat = Catter(args.files, args.number)
 99 |         cat.run(sys.stdout)
100 |         logging.debug('done catting')
101 | 
102 | if __name__ == '__main__':
103 |     main(sys.argv[1:])
104 | 


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