Use argparse to produce nicer CLI

blah/commands.py

@@ -5,24 +5,30 @@
 import blah.repositories
 import blah.fetcher
 
-def find_command(name):
-    return commands[name]
+class WhatIsThisCommand(object):
+    def create_parser(self, subparser):
+        subparser.add_argument("directory", nargs="?")
+
+    def execute(self, args):
+        directory = args.directory if args.directory is not None else os.getcwd()
+        repository = blah.repositories.find_repository(directory)
+        if repository is None:
+            print "Could not find source control repository"
+        else:
+            print "{0}+file://{1}".format(repository.type, repository.working_directory)
 
-def what_is_this_command():
-    directory = sys.argv[2] if len(sys.argv) > 2 else os.getcwd()
-    repository = blah.repositories.find_repository(directory)
-    if repository is None:
-        print "Could not find source control repository"
-    else:
-        print "{0}+file://{1}".format(repository.type, repository.working_directory)
+what_is_this_command = WhatIsThisCommand()
 
-def fetch_command():
-    repository_uri = sys.argv[2]
-    local_path = sys.argv[3]
-    blah.fetcher.fetch(repository_uri, local_path)
+class FetchCommand(object):
+    def create_parser(self, subparser):
+        subparser.add_argument("repository_uri", metavar="repository-uri")
+        subparser.add_argument("local_path", metavar="local-path")
+
+    def execute(self, args):
+        blah.fetcher.fetch(args.repository_uri, args.local_path)
 
 commands = {
     "whatisthis": what_is_this_command,
     "what-is-this": what_is_this_command,
-    "fetch": fetch_command
+    "fetch": FetchCommand()
 }

requirements.txt

@@ -1,2 +1,3 @@
+argparse==1.2.1
 nose==1.2.1
 mock==0.8.0

scripts/blah

@@ -1,16 +1,22 @@
 #!/usr/bin/env python
 
 import sys
+import argparse
+import functools
 
-from blah.commands import find_command
+from blah.commands import commands
 
 def main():
-    command_name = sys.argv[1]
-    command = find_command(command_name)
-    if command is None:
-        print 'command not recognised: {0}'.format(command_name)
-    else:
-        command()
+    parser = argparse.ArgumentParser()
+    subparsers = parser.add_subparsers()
+
+    for command_name, command in commands.iteritems():
+        subparser = subparsers.add_parser(command_name)
+        subparser.set_defaults(func=command.execute)
+        command.create_parser(subparser)
+
+    args = parser.parse_args()
+    args.func(args)
 
 if __name__ == "__main__":
     main()

setup.py

@@ -15,4 +15,5 @@ def read(fname):
     url='http://github.com/mwilliamson/blah',
     scripts=["scripts/blah"],
     packages=['blah'],
+    install_requires=["argparse==1.2.1"],
 )