Python: Parent Class not recognizing __init_

Python: Parent Class not recognizing init of its subclasses

I have been working with inheritance, but I got confused as to why my parent class is not recognizing the init of my sub classes. Here is an example of my code that is giving me none when run, when it shouldn't.

class Coins(object):

    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 

class US_Coins(Coins):

    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]

class Metric_Coins(Coins):

    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]

metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

asked Nov 20 '18 at 6:15

John Doe

1

Inheritance works upwards, not downwards. Meaning Metric_Coins will inherit properties from Coins. But Coins won't inherit anything from anyone. Meaning Coins won't get any values or properties from any of the other classes. One such variable is self._coins which is only created in two of the classes, but never defined in Coins. As @antona pointed out correctly. this shows a basic concept of how this works.

– Torxed
Nov 20 '18 at 6:33

2

You should add a return change to your make_changemethod so that it gives you an output. Also, only subclasses can get methods from their parents and not the other way around.

– N Chauhan
Nov 20 '18 at 6:43

Can you clarify what your problem is? A parent class is not meant to do anything with methods of its subclasses. Even in your case, it would not make sense if Coins were to use __init__ of its subclasses - the two are not compatible. Would Coins()._coins be [50, 25, 10, 5, 1] or [50, 20, 10, 5, 2, 1]?

– MisterMiyagi
Nov 20 '18 at 10:17

add a comment |

class Coins(object):

    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 

class US_Coins(Coins):

    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]

class Metric_Coins(Coins):

    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]

metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

asked Nov 20 '18 at 6:15

John Doe

1

Inheritance works upwards, not downwards. Meaning Metric_Coins will inherit properties from Coins. But Coins won't inherit anything from anyone. Meaning Coins won't get any values or properties from any of the other classes. One such variable is self._coins which is only created in two of the classes, but never defined in Coins. As @antona pointed out correctly. this shows a basic concept of how this works.

– Torxed
Nov 20 '18 at 6:33

2

You should add a return change to your make_changemethod so that it gives you an output. Also, only subclasses can get methods from their parents and not the other way around.

– N Chauhan
Nov 20 '18 at 6:43

Can you clarify what your problem is? A parent class is not meant to do anything with methods of its subclasses. Even in your case, it would not make sense if Coins were to use __init__ of its subclasses - the two are not compatible. Would Coins()._coins be [50, 25, 10, 5, 1] or [50, 20, 10, 5, 2, 1]?

– MisterMiyagi
Nov 20 '18 at 10:17

add a comment |

class Coins(object):

    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 

class US_Coins(Coins):

    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]

class Metric_Coins(Coins):

    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]

metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

asked Nov 20 '18 at 6:15

John Doe

class Coins(object):

    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 

class US_Coins(Coins):

    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]

class Metric_Coins(Coins):

    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]

metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

python inheritance

asked Nov 20 '18 at 6:15

John Doe

asked Nov 20 '18 at 6:15

John Doe

asked Nov 20 '18 at 6:15

John Doe

asked Nov 20 '18 at 6:15

John Doe

asked Nov 20 '18 at 6:15

John Doe

1

Inheritance works upwards, not downwards. Meaning Metric_Coins will inherit properties from Coins. But Coins won't inherit anything from anyone. Meaning Coins won't get any values or properties from any of the other classes. One such variable is self._coins which is only created in two of the classes, but never defined in Coins. As @antona pointed out correctly. this shows a basic concept of how this works.

– Torxed
Nov 20 '18 at 6:33

2

You should add a return change to your make_changemethod so that it gives you an output. Also, only subclasses can get methods from their parents and not the other way around.

– N Chauhan
Nov 20 '18 at 6:43

Can you clarify what your problem is? A parent class is not meant to do anything with methods of its subclasses. Even in your case, it would not make sense if Coins were to use __init__ of its subclasses - the two are not compatible. Would Coins()._coins be [50, 25, 10, 5, 1] or [50, 20, 10, 5, 2, 1]?

– MisterMiyagi
Nov 20 '18 at 10:17

add a comment |

1

Inheritance works upwards, not downwards. Meaning Metric_Coins will inherit properties from Coins. But Coins won't inherit anything from anyone. Meaning Coins won't get any values or properties from any of the other classes. One such variable is self._coins which is only created in two of the classes, but never defined in Coins. As @antona pointed out correctly. this shows a basic concept of how this works.

– Torxed
Nov 20 '18 at 6:33

2

You should add a return change to your make_changemethod so that it gives you an output. Also, only subclasses can get methods from their parents and not the other way around.

– N Chauhan
Nov 20 '18 at 6:43

Can you clarify what your problem is? A parent class is not meant to do anything with methods of its subclasses. Even in your case, it would not make sense if Coins were to use __init__ of its subclasses - the two are not compatible. Would Coins()._coins be [50, 25, 10, 5, 1] or [50, 20, 10, 5, 2, 1]?

– MisterMiyagi
Nov 20 '18 at 10:17

Inheritance works upwards, not downwards. Meaning Metric_Coins will inherit properties from Coins. But Coins won't inherit anything from anyone. Meaning Coins won't get any values or properties from any of the other classes. One such variable is self._coins which is only created in two of the classes, but never defined in Coins. As @antona pointed out correctly. this shows a basic concept of how this works.

– Torxed
Nov 20 '18 at 6:33

You should add a return change to your make_changemethod so that it gives you an output. Also, only subclasses can get methods from their parents and not the other way around.

– N Chauhan
Nov 20 '18 at 6:43

Can you clarify what your problem is? A parent class is not meant to do anything with methods of its subclasses. Even in your case, it would not make sense if Coins were to use __init__ of its subclasses - the two are not compatible. Would Coins()._coins be [50, 25, 10, 5, 1] or [50, 20, 10, 5, 2, 1]?

– MisterMiyagi
Nov 20 '18 at 10:17

add a comment |

1 Answer
1

active

oldest

votes

You need to define self._coins field in Coins class. Without it, function make_change cannot be executed because it evokes field that does not exist in this parent class (for coin in (self._coins)).

Edited: in order to achieve your goal you need to create a field inside Coins class:

class Coins(object):



    def __init__self():

        self._coins = 



    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 





class US_Coins(Coins):



    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]





class Metric_Coins(Coins):



    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]





metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

Now you are able to operate with make_change method on the us and metric; and also on coins object.

edited Nov 20 '18 at 14:48

answered Nov 20 '18 at 6:18

artona

71247

Thank you, is there any way to account for the changing self._coins ([50, 25, 10, 5, 1] and [50, 20, 10, 5, 2, 1]) in the Coins class?

– John Doe
Nov 20 '18 at 7:03

@JohnDoe made update

– artona
Nov 20 '18 at 10:12

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

Edited: in order to achieve your goal you need to create a field inside Coins class:

class Coins(object):



    def __init__self():

        self._coins = 



    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 





class US_Coins(Coins):



    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]





class Metric_Coins(Coins):



    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]





metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

Now you are able to operate with make_change method on the us and metric; and also on coins object.

edited Nov 20 '18 at 14:48

answered Nov 20 '18 at 6:18

artona

71247

Thank you, is there any way to account for the changing self._coins ([50, 25, 10, 5, 1] and [50, 20, 10, 5, 2, 1]) in the Coins class?

– John Doe
Nov 20 '18 at 7:03

@JohnDoe made update

– artona
Nov 20 '18 at 10:12

add a comment |

Edited: in order to achieve your goal you need to create a field inside Coins class:

class Coins(object):



    def __init__self():

        self._coins = 



    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 





class US_Coins(Coins):



    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]





class Metric_Coins(Coins):



    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]





metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

Now you are able to operate with make_change method on the us and metric; and also on coins object.

edited Nov 20 '18 at 14:48

answered Nov 20 '18 at 6:18

artona

71247

Thank you, is there any way to account for the changing self._coins ([50, 25, 10, 5, 1] and [50, 20, 10, 5, 2, 1]) in the Coins class?

– John Doe
Nov 20 '18 at 7:03

@JohnDoe made update

– artona
Nov 20 '18 at 10:12

add a comment |

Edited: in order to achieve your goal you need to create a field inside Coins class:

class Coins(object):



    def __init__self():

        self._coins = 



    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 





class US_Coins(Coins):



    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]





class Metric_Coins(Coins):



    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]





metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

Now you are able to operate with make_change method on the us and metric; and also on coins object.

edited Nov 20 '18 at 14:48

answered Nov 20 '18 at 6:18

artona

71247

Edited: in order to achieve your goal you need to create a field inside Coins class:

class Coins(object):



    def __init__self():

        self._coins = 



    def make_change(self, amount):

        change = 

        for coin in (self._coins):

            change.append(amount // coin)

            amount = amount - change[-1] * coin 





class US_Coins(Coins):



    def __init__(self):

        self._coins = [50, 25, 10, 5, 1]





class Metric_Coins(Coins):



    def __init__(self):

        self._coins = [50, 20, 10, 5, 2, 1]





metric = Metric_Coins()

us = US_Coins()

print(us.make_change(73))

print(metric.make_change(73))

coins = Coins()

print(coins.make_change(27))

Now you are able to operate with make_change method on the us and metric; and also on coins object.

edited Nov 20 '18 at 14:48

answered Nov 20 '18 at 6:18

artona

71247

edited Nov 20 '18 at 14:48

answered Nov 20 '18 at 6:18

artona

71247

answered Nov 20 '18 at 6:18

artona

71247

answered Nov 20 '18 at 6:18

artona

71247

Thank you, is there any way to account for the changing self._coins ([50, 25, 10, 5, 1] and [50, 20, 10, 5, 2, 1]) in the Coins class?

– John Doe
Nov 20 '18 at 7:03

@JohnDoe made update

– artona
Nov 20 '18 at 10:12

add a comment |

Thank you, is there any way to account for the changing self._coins ([50, 25, 10, 5, 1] and [50, 20, 10, 5, 2, 1]) in the Coins class?

– John Doe
Nov 20 '18 at 7:03

@JohnDoe made update

– artona
Nov 20 '18 at 10:12

Thank you, is there any way to account for the changing self._coins ([50, 25, 10, 5, 1] and [50, 20, 10, 5, 2, 1]) in the Coins class?

– John Doe
Nov 20 '18 at 7:03

@JohnDoe made update

– artona
Nov 20 '18 at 10:12

add a comment |

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