CODEWITHSUNDEEP
pythonfunctionsyntaxarguments
Горячев Дмитрий
Горячев Дмитрий

Reputation: 68

Pass required argument to optional

Trying to make a board, which must be a square if there as only one argument (and a rectangle if there are two of them).

Code sample:

class Game:
    def __init__(self,h,w=h): # lookie-lookie 
       self.board = [[0 for i in range(w)] for j in range(h)]

What I expect:

b = Game(2)
b.board
#should return [[0,0],[0,0]]
b = Game(2,1)
b.board
#should return [[0],[0]]

What i got:

NameError: name 'h' is not defined

How should I fix it?

Upvotes: 1

Views: 40

Answers (1)

Moses Koledoye
Moses Koledoye

Reputation: 78546

At function definition, the value passed to optional arguments is evaluated, however, in that instant, h is not defined. You can instead use a sentinel value as a placeholder for the optional argument:

class Game(object):
    def __init__(self,h,w=None):
        if w is None:
           w = h

If you're on Python 2, remember to subclass object.

Upvotes: 3

Related Questions