Python recursive return using dict.get

Question

I'm writting a code for rock scissor paper game. But when I run it, it falls into infinite loop.

The problem happened in following code. Why this code result in infinite loop for any input value? (my python version is 3.5.0)

class Peoples(object):            
    def recept(self):
        u = input('choose..r or s or p: ')
        print('choice: ',{'r':'rock','s':'scissor','p':'p'}.get(u,'{} (wrong input)'.format(u)))
        return {'s':0,'r':1,'p':2}.get(u,self.recept())

P=Peoples()
P.recept()

Kevin · Accepted Answer · 2016-01-06 20:21:48Z

1

Because the second argument of get gets executed regardless of whether it will ultimately be used by get. You ought to break it up into multiple lines so it only recursively calls when necessary:

d = {'s':0,'r':1,'p':2}
if u in d:
    return d[u]
else:
    return self.recept()

But really, it would be preferable to not use recursion at all, since you'll hit the maximum recursion depth and crash after the user chooses an invalid input enough times in a row.

def recept(self):
    d = {'s':0,'r':1,'p':2}
    while True:
        u = input('choose..r or s or p: ')
        print('choice: ',{'r':'rock','s':'scissor','p':'p'}.get(u,'{} (wrong input)'.format(u)))
        if u in d:
            return d[u]

answered Jan 6, 2016 at 20:21

Kevin

76.5k13 gold badges141 silver badges168 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Python recursive return using dict.get

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related