Python Notes: Difference between revisions
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== Start == | |||
Docs: | Docs: | ||
* Latest: docs.python.org | * Latest: docs.python.org | ||
* Old release http://docs.python.org/release/2.2.1/lib/module-cgi.html | * Old release http://docs.python.org/release/2.2.1/lib/module-cgi.html | ||
* formatting https://pyformat.info/ | |||
'{:>10}'.format('test') # padding | |||
'{} {}'.format('one', 'two') | |||
'{0!s} {0!r}'.format(Data()) # forms | |||
'{:.5}'.format('xylophone') # truncate | |||
== ghetto command line argv == | == ghetto command line argv == |
Revision as of 16:25, 21 December 2017
Start
Docs:
- Latest: docs.python.org
- Old release http://docs.python.org/release/2.2.1/lib/module-cgi.html
- formatting https://pyformat.info/
'{:>10}'.format('test') # padding
'{} {}'.format('one', 'two')
'{0!s} {0!r}'.format(Data()) # forms
'{:.5}'.format('xylophone') # truncate
ghetto command line argv
#!/usr/bin/python import sys print 'Number of arguments:', len(sys.argv), 'arguments.' print 'Argument List:', str(sys.argv)
Less ghetto argparse
import argparse parser = argparse.ArgumentParser() parser.add_argument('access_key', help='Access Key'); parser.add_argument('secret_key', help='Secret Key'); args = parser.parse_args() global access_key global secret_key access_key = args.access_key secret_key = args.secret_key
what's in that object?
https://download.tuxfamily.org/jeremyblog/diveintopython-5.4/py/apihelper.py
then use it like this:
#!/usr/bin/env python from apihelper import info mything info(mything)
AutoVivification
import pprint class Vividict(dict): def __missing__(self, key): value = self[key] = type(self)() return value d = Vividict() d['foo']['bar'] d['foo']['baz'] d['fizz']['buzz'] d['primary']['secondary']['tertiary']['quaternary'] pprint.pprint(d)
vim tabs
in file:
# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
in ~/.vimrc:
tabstop=8 expandtab shiftwidth=4 softtabstop=4
parse json
python -m json.tool my_json.json
parse yaml
python -c "from yaml import load, Loader; load(open('filename.yml'), Loader=Loader)"
urllib
https://stackoverflow.com/questions/3238925/python-urllib-urllib2-post
datetime
stuff
def last_day_of_month(any_day): next_month = any_day.replace(day=28) + datetime.timedelta(days=4) # this will never fail return next_month - datetime.timedelta(days=next_month.day)
tuples
>>> x = [(1,2), (3,4), (5,6)] >>> for item in x: ... print "A tuple", item A tuple (1, 2) A tuple (3, 4) A tuple (5, 6) >>> for a, b in x: ... print "First", a, "then", b First 1 then 2 First 3 then 4 First 5 then 6
Exception handling
try: # rv, data = M.search(None, "ALL") # rv, data = M.search(None, 'SENTSINCE 1-Jan-2017 SENTBEFORE 31-Dec-2017') rv, data = M.search(None, 'SENTSINCE 1 Jan 2017') except Exception, e: print "M.search failed" print "Error %s" % M.error.message print "Exception is %s" % str(e)
also:
try: pass except Exception as e: # Just print(e) is cleaner and more likely what you want, # but if you insist on printing message specifically whenever possible... if hasattr(e, 'message'): print(e.message) else: print(e)
Pretty Printer
import pprint pp = pprint.PrettyPrinter(indent=4) pp.pprint(stuff)
Tag extract
I have no idea why this works:
you get an instance from boto3 aws describe_instances and you want _one_ tag:
retention_days = [ int(t.get('Value')) for t in instance['Tags'] if t['Key'] == 'snapshot_retention'][0]