Passing function as an argument: Python

Question

As functions in Python are objects so we can pass them into other functions. For example:

def hello(x) :
    return "Hello World"*x
def bye(x) :
    return "Bye World"*x
def analyze(func,x) :
    return func(x)

For analyze(bye, 3) OUTPUT is Bye WorldBye WorldBye World

For analyze(hello, 3) OUTPUT is Bye World WorldHello World

It makes sense but while doing the same in-class Objects it throws an error. For example:

class Greetings:
   def __init__(self):
      pass
   def hello(self, x) :
      return "Hello World"*x
   def bye(self, x) :
      return "Bye World"*x
   def analyze(self, func, x) :
      return self.func(x)

Driver Code:

obj = Greetings()
obj.analyze(hello, 3)

Throws TypeError: analyze() missing 1 required positional argument: 'x'

I even tried obj.analyze(obj, hello, 3)

Then it throws AttributeError: type object 'Greetings' has no attribute 'func' exception.

`self.func` accesses the attribute literally named `func`, which doesn't exist. Also you're passing the previously-defined `func` function, not the name of the method you want to call (i.e. a string). The dupe tells you how to access the method by name, but you'll have to change what you're calling `obj.analyze` with too. — jonrsharpe, Oct 14 '20 at 11:34
I get "Name error: 'hello' not defined". it should be `obj.hello` or `Greetings.hello`. (Or if the other functions are still in scope, you should get "'Greetings' object has no attribute 'func'".) — tobias_k, Oct 14 '20 at 11:35
Actually, your errors sound more like you accidentally did `obj = Greetings` instead of `obj = Greetings()` — tobias_k, Oct 14 '20 at 11:38

score 0 · Accepted Answer · answered Oct 14 '20 at 11:35

Can you try this,

class Greetings:
   def __init__(self):
      pass

   def hello(self, x) :
      return "Hello World"*x

   def bye(self, x) :
      return "Bye World"*x

   def analyze(self, func, x) :
      return func(x)

obj = Greetings()
print(obj.analyze(obj.hello, 3))

score 0 · Answer 2 · edited Oct 14 '20 at 12:08

0

class Greetings:
   def __init__(self):
      pass
   def hello(self, x) :
      return "Hello World"*x
   def bye(self, x) :
      return "Bye World"*x
   def analyze(self, func, x) :
      return func(x)

obj = Greetings()
obj.analyze(obj.hello, 3)

edited Oct 14 '20 at 12:08

Sergey Shubin

3,040
4
24
36

answered Oct 14 '20 at 11:41

Glenn

1

1

Please add explanation for quality and long term value. – SherylHohman Oct 14 '20 at 15:05
You used return self.func(x) but you your class has no function named func. – Glenn Oct 15 '20 at 13:56
hello is inside a class so you use instance of class.function – Glenn Oct 15 '20 at 13:58

Passing function as an argument: Python

2 Answers2