initializing variable while defining function in python?

Question

Learning Python, trying to read NASA program. Why is it show=True while defining function? Are we allowed to initialize variable this way? I don' see any use of it.

def visualizeDomain(domain, show=True):
    '''Draw all the sensors and ground truth from a domain'''
    centerMap(domain.center[0], domain.center[1], 11)
    for s in domain.sensor_list:
        apply(addToMap, s.visualize(show=show))
    if domain.ground_truth != None:
        addToMap(domain.ground_truth, {}, 'Ground Truth', False)

Thank you everyone for your help.

docs.python.org/2/tutorial/…

BrenBarn
– BrenBarn

2015-01-19 04:37:41 +00:00
Commented Jan 19, 2015 at 4:37 — BrenBarn
– BrenBarn, Commented Jan 19, 2015 at 4:37
it's passed to s.visualize() on the fourth line

Eevee
– Eevee

2015-01-19 04:46:06 +00:00
Commented Jan 19, 2015 at 4:46 — Eevee
– Eevee, Commented Jan 19, 2015 at 4:46

Eevee · Accepted Answer · 2015-01-19 04:45:21Z

5

This is Python's syntax for default arguments. If no value is passed for the second argument to visualizeDomain(), it will automatically be assigned a value of True. (See https://docs.python.org/2/tutorial/controlflow.html#default-argument-values)

edited Jan 19, 2015 at 4:45

Eevee

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answered Jan 19, 2015 at 4:42

jgray

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1 Comment

Mark Ransom Over a year ago

And note that it is evaluated when defining the function, so if the value is mutable and you change it inside the function, the change holds for the next invocation of the function. Doesn't apply in this case since True is immutable.

Chris Nguyen · Accepted Answer · 2015-01-19 04:51:51Z

0

So yeah, all the answers are right. Basically you can call that function with just one argument... "Show" will just be True.

answered Jan 19, 2015 at 4:51

Chris Nguyen

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