Object-oriented programming (python)

Question

class Ammo(Thing):
    def __init__(self, name, weapon, quantity):
        self.name=name
        self.weapon=weapon
        self.quantity=quantity
    def get_quantity(self):
        return self.quantity
    def weapon_type(self):
        return self.weapon
    def remove_all():
        self.quantity=0

bow = Weapon('bow', 10, 20)
arrows = Ammo('arrow', bow, 5)
print(arrows.weapon_type())

output of print(arrows.weapon_type()) is supposed to be bow but I got <__main__.Weapon object at 0x10441f0b8> instead. How can I modify my code so that it returns bow?

Below is class Weapon:

import random
class Weapon(Thing):
    def __init__(self, name, min_dmg, max_dmg):
        self.name=name
        self.min_dmg=min_dmg
        self.max_dmg=max_dmg
    def min_damage(self):
        return self.min_dmg
    def max_damage(self):
        return self.max_dmg
    def damage(self):
        return random.randint(self.min_dmg,self.max_dmg)

Try `return self.weapon.name` inside `weapon_type`. You are returning (and then printing) the *entire* `Weapon` object instead of just the name. — gen_Eric, Mar 29 '17 at 16:43
Possible duplicate of [How to print a class or objects of class using print()?](http://stackoverflow.com/questions/1535327/how-to-print-a-class-or-objects-of-class-using-print) — Yang, Mar 29 '17 at 16:48

score 1 · Answer 1 · answered Mar 29 '17 at 16:50

1

I think the best way to do it would be overriding the str function in Weapon.

adding:

def __str__(self):
    return self.name

to your weapon class should fix it.

answered Mar 29 '17 at 16:50

NK_loco

84
7

score 1 · Answer 2 · answered Mar 29 '17 at 17:13

It depends on what do you want to print.

bow = Weapon('bow', 10, 20)
arrows = Ammo('arrow', bow, 5)
print(arrows.weapon_type())

The name of object:

bow = Weapon('bow', 10, 20)
#               \_______ name of object

so you have to:

print(arrows.weapon_type().name)
# it will print bow

or your object itself:

bow = Weapon('bow', 10, 20)
#  \____________________ object

I personally prefer print the name I passed in arguments, so if I call my object bow and pass "hardened_bow", 10, 20 as arguments it will print "hardened_bow" and not "bow"

score 0 · Answer 3 · answered Mar 29 '17 at 16:57

Add repr to Weapon class:

def __repr__(self):
    return self.name

object.__repr__(self)

Called by the repr() built-in function and by string conversions (reverse quotes) to compute the “official” string representation of an object. If at all possible, this should look like a valid Python expression that could be used to recreate an object with the same value (given an appropriate environment).

If this is not possible, a string of the form <...some useful description...> should be returned. The return value must be a string object. If a class defines repr() but not str(), then repr() is also used when an “informal” string representation of instances of that class is required.

This is typically used for debugging, so it is important that the representation is information-rich and unambiguous.

object.__str__(self)

Called by the str() built-in function and by the print statement to compute the “informal” string representation of an object. This differs from __repr__() in that it does not have to be a valid Python expression: a more convenient or concise representation may be used instead. The return value must be a string object.

Reference

Object-oriented programming (python)

3 Answers3