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""" Module doc string if you import this module and do help (module) you'll see this |
"""Module summary If you import this module and do help (module) you'll see this. The first line of a docstring is the "summary", and should be a one line description. You can go into more detail after the summary if needed. See http://www.python.org/dev/peps/pep-0257/ for the python docstring style guide. |
This represents our best thinking about how to start your python script.
(Though you probably want to remove the excess comments).
1 #!/usr/bin/env python
2
3 # #!/usr/bin/env python - will search for the first python
4 # interpreter on your path
5 # unlike
6 # #!/usr/bin/python2.5 - which will only run if there is a file
7 # python 2.5 is installed at /usr/bin
8
9 """Module summary
10
11 If you import this module and do help (module) you'll see this.
12 The first line of a docstring is the "summary", and should be
13 a one line description.
14
15 You can go into more detail after the summary if needed.
16 See http://www.python.org/dev/peps/pep-0257/
17 for the python docstring style guide.
18 """
19
20 # optparse is both easy to use and produces clean code
21 # the main optparse docs can be found here:
22 # http://docs.python.org/library/optparse.html
23 # there's a much better tutorial that works you through optparse
24 # starting with a simple example and slowly adding complexity.
25 from optparse import OptionParser
26 import sys
27
28
29 def main(cmdline=None):
30 """Example main function.
31
32 If cmdline is none, parser.parse_args will look at
33 sys.argv[1:] by default
34
35 However if import this module in python call this main function
36 like this:
37
38 main(["-n", "3", "asdf", "jkl"])
39
40 in addition to running it from the shell.
41 """
42 parser = make_parser()
43
44 opts, args = parser.parse_args(cmdline)
45
46 if opts.error is not None:
47 return opts.error
48 elif opts.bad_option:
49 # you can call parser.error, which will show an error message
50 # displays the help, and then exits the program
51 parser.error("you called a bad option")
52
53 # args is now just a list, of everything that wasn't an
54 # "option". AKA everything that started with - or --
55 for i in range(len(args)):
56 print "arg %d: %s" % (i, args[i])
57
58 print "the number is:", opts.number
59 # opts.number is always defined, as I set a default value
60 # up in the make_parser
61
62 return 0
63
64
65 def make_parser():
66 """Construct an option parser
67 """
68 usage = """%prog: args
69
70 Sometimes you might explain the purpose of this program as well.
71 """
72
73 parser = OptionParser(usage)
74
75 # add_options takes at least one long option
76 # you can optionally include a short option.
77 # - are one character (short) options (e.g. -h)
78 #
79 # -- are long options, the name is also used as the
80 # variable name attached that holds the option
81
82 parser.add_option("-e", "--error", help="set error code")
83
84 # opt_parse can be configured to store different kinds of values
85 # like filenames, and boolean options
86 parser.add_option("-b", "--bad-option", action="store_true",
87 help="trigger an option error")
88
89 # you can also do simple type checking on parameters
90 parser.add_option("-n", "--number", help="set a number", type="int")
91
92 # if needed you can tell optparse to use a different variable name.
93 # with the dest argument.
94 parser.add_option("--index", dest="createRDSIndex", action="store_true")
95
96 parser.set_defaults(bad_option=False,
97 createRDSIndex=False,
98 error=None,
99 number=0)
100
101 return parser
102
103
104 if __name__ == "__main__":
105 # this runs when the application is run from the command
106 # it grabs sys.argv[1:] which is everything after the program name
107 # and passes it to main
108 # the return value from main is then used as the argument to
109 # sys.exit, which you can test for in the shell.
110 # program exit codes are usually 0 for ok, and non-zero for something
111 # going wrong.
112 sys.exit(main(sys.argv[1:]))
113
114 # Try the following examples
115 # python script_template.py
116 # python script_template.py --help
117 # ./script_template.py a b c
118 # ./script_template.py --bad-option
119 # python ./script_template.py -n 4
120 # python ./script_template.py --number foo
121
122
123
124 # Guido von Rossum (inventor of python) has this write up on how to
125 # write a main
126 # http://www.artima.com/weblogs/viewpost.jsp?thread=4829
127 # however he used the older getopt module which isn't as easy
128 # to configure as optparse