Defining a function,
MyFunction(argument, *args): [do something to argument[arg] for arg in *args]
if *args is empty, the function doesn't do anything, but I want to make the default behavior 'use the entire set if length of *args == 0'
def Export(source, target, *args, sep=','):
for item in source:
SubsetOutput(WriteFlatFile(target), args).send(item[0])
I don't want to check the length of args on every iteration, and I can't access the keys of item in source until the iteration begins...
so i could
if len(args) != 0:
for item in source:
else
for item in source:
which will probably work but doesn't seem 'pythonic' enough?
is this (is there) a standard way to approach *args or **kwargs and default behavior when either is empty?
More Code:
def __coroutine(func):
"""
a decorator for coroutines to automatically prime the routine
code and method from 'curous course on coroutines and concurrency'
by david beazley www.dabeaz.com
"""
def __start(*args, **kwargs):
cr = func(*args, **kwargs)
next(cr)
return cr
return __start
def Export(source, target, *args, sep=','):
if args:
for item in source:
SubsetOutput(WriteFlatFile(target, sep), args).send(item)
else:
for item in source:
WriteFlatFile(target, sep).send(item)
@__coroutine
def SubsetOutput(target, *args):
"""
take *args from the results and pass to target
TODO
----
raise exception when arg is not in result[0]
"""
while True:
result = (yield)
print([result.arg for arg in result.dict() if arg in args])
target.send([result.arg for arg in result.dict if arg in args])
@__coroutine
def WriteFlatFile(target, sep):
"""
take set of results to a flat file
TODO
----
"""
filehandler = open(target, 'a')
while True:
result = (yield)
line = (sep.join([str(result[var]) for
var in result.keys()])).format(result)+'\n'
filehandler.write(line)
Is there a way to pass an "entire set" argument to SubsetOutput
, so you can bury the conditional inside its call rather than have an explicit if
? This could be None
or []
, for example.
# Pass None to use full subset.
def Export(source, target, *args, sep=','):
for item in source:
SubsetOutput(WriteFlatFile(target), args or None).send(item[0])
# Pass an empty list [] to use full subset. Even simpler.
def Export(source, target, *args, sep=','):
for item in source:
SubsetOutput(WriteFlatFile(target), args).send(item[0])
If not, I would go with the two loop solution, assuming the loop really is a single line. It reads well and is a reasonable use case for a little bit of code duplication.
def Export(source, target, *args, sep=','):
if args:
for item in source:
SubsetOutput(WriteFlatFile(target), args).send(item[0])
else:
for item in source:
FullOutput(WriteFlatFile(target)).send(item[0])