CODEWITHSUNDEEP
pythonfunctionparameters
kamikaze_pilot
kamikaze_pilot

Reputation: 14834

python function parameter screwing up

so I have 

def gcd(a,b):
    if a == 0:
            return b
    while b != 0:
            if a > b:
                    a = a - b
            else:
                    b = b - a
    return a

but then when I call gcd(1,2) from the console, the error

Traceback (most recent call last): File "", line 1, in G.gcd(1,2) TypeError: gcd() takes exactly 2 arguments (3 given)

comes up....

which makes no sense at all since I only gave 2 arguments...

what did I do wrong?

allright so I deleted everything else and this is the only thing in my class: 

import random
import math

class RSA:
    def gcd(a,b):
        if a == 0:
            return b
        while b != 0:
            if a > b:
                a = a - b
            else:
                b = b - a
        return a

and the problem still persists

Upvotes: 1

Views: 251

Answers (8)

Cristian Ciupitu
Cristian Ciupitu

Reputation: 20860

You could use the staticmethod decorator like this:

...
class RSA:    

    @staticmethod
    def gcd(a,b):
        ...

Upvotes: 3

shang
shang

Reputation: 24802

There's already an accepted answer that solves the problem, but I'd like to point out, that (IMHO) a more idiomatic solution in Python would be to move the gcd method outside the class to a plain function in the module.

I mean, it's a general purpose function. There's no reason in Python to encapsulate it in a class.

Upvotes: 1

SingleNegationElimination
SingleNegationElimination

Reputation: 156138

You have not posted all of your code. The code you didn't post looks like this:

class SomeClass:

    def gcd(a,b):
        if a == 0:
                return b
        while b != 0:
                if a > b:
                        a = a - b
                else:
                        b = b - a
        return a 

G = SomeClass()
G.gcd(1,2)

In python, when you define a class member function, the class instance is automatically passed to the function. Change your code to look like this:

class SomeClass:

    def gcd(a,b):
        if a == 0:
                return b
        while b != 0:
                if a > b:
                        a = a - b
                else:
                        b = b - a
        return a 

G = SomeClass()
G.gcd(1,2)

or better yet

def gcd( a,b):
    if a == 0:
            return b
    while b != 0:
            if a > b:
                    a = a - b
            else:
                    b = b - a
    return a 

gcd(1,2)

and all will be well.

Upvotes: 5

Eddie Flores
Eddie Flores

Reputation: 1103

The code as you provide it, works fine in an interpreter. If you're calling gcd() as a method, you need to add "self" as first argument.

    def gcd(self, a, b):
        //...

Upvotes: 0

Asterisk
Asterisk

Reputation: 3574

if gcd is a method inside the class then you should define it as follows:

def gcd(self, a, b): etc.

Upvotes: 2

jpsimons
jpsimons

Reputation: 28090

You're calling the function as a method. Add "self" as the first argument and it'll work.

Upvotes: 7

SpliFF
SpliFF

Reputation: 38956

I suspect (since the error is in code you haven't provided) that gcd is actually a method and you are calling it as obj.gcd(a,b). This is translated as gcd(self, a, b) = 3 arguments. you need to define the function with the self argument.

Upvotes: 1

John Chadwick
John Chadwick

Reputation: 3213

I just threw that code into Python (in interpreter mode) and it seems to work just fine. Are you sure gcd isn't being redefined anywhere? Python will allow you to redefine functions without warning, if I remember correctly.

Upvotes: 0

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