Calling an argument in a python function as part of the function definition?

Question

How can I pass an argument in a function input within the function definition?

For example:

def correlate1(vara1, vara2=vara1*2):
    print "test"

Returns:

Traceback (most recent call last):
  File "test.py", line 321, in <module>
    def correlate1(vara1, vara2=vara*2):
NameError: name 'vara1' is not defined

Obviously, you could do this:

    def correlate1(vara1, vara2=0):
        if vara2==0:
            var2=vara1*2        
        print "test"

But is there a way to do it in the function definition?

Blender · Accepted Answer · 2012-06-04 17:51:52Z

7

Just set it once the function is called:

def correlate1(vara1, vara2=None):
    vara2 = 2 * vara1 if vara2 is None else vara2

    print "test"

or even more simple:

def correlate2(var1, var2=None):
    var2 = var2 or var1 * 2
    print "test"

var2's default value expression can not contain var1 because var1 does not exist until the function is called.

edited Jun 4, 2012 at 17:51

answered Jun 4, 2012 at 17:03

Blender

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1 Comment

catchmeifyoutry Over a year ago

+1 because this answer is using None, instead of 0 as the questioner mentioned, to indicate that the 'default interpretation' of vara2 should be used. This matters since vara2 is expected to be a numeric value, thus when called with vara2=0 this could actually be the intended value.

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