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Clean-up example

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Raymond Hettinger 2012-07-15 23:53:32 -07:00
parent 4866266bf4
commit b2269baca3
1 changed files with 11 additions and 5 deletions
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16
Doc/library/collections.rst
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@ -130,16 +130,22 @@ Example of simulating Python's internal lookup chain::
import builtins import builtins
pylookup = ChainMap(locals(), globals(), vars(builtins)) pylookup = ChainMap(locals(), globals(), vars(builtins))
Example of letting user specified values take precedence over environment Example of letting user specified command-line arguments take precedence over
variables which in turn take precedence over default values:: environment variables which in turn take precedence over default values::
import os, argparse import os, argparse
defaults = {'color': 'red', 'user': guest}
defaults = {'color': 'red', 'user': 'guest'}
parser = argparse.ArgumentParser() parser = argparse.ArgumentParser()
parser.add_argument('-u', '--user') parser.add_argument('-u', '--user')
parser.add_argument('-c', '--color') parser.add_argument('-c', '--color')
user_specified = vars(parser.parse_args()) namespace = parser.parse_args()
combined = ChainMap(user_specified, os.environ, defaults) command_line_args = {k:v for k, v in vars(namespace).items() if v}
combined = ChainMap(command_line_args, os.environ, defaults)
print(combined['color'])
print(combined['user'])
Example patterns for using the :class:`ChainMap` class to simulate nested Example patterns for using the :class:`ChainMap` class to simulate nested
contexts:: contexts::