Use a decorator to turn a function into a generator in Python -

is there way decorator convert function below generator?

@decorator_that_makes_func_into_generator def countdown(n):     while n > 0:         print n,         n = n - 1 

the function can modified if necessary. note function not have yield statement, otherwise generator.

if can't change source of countdown, you'll have capture output:

import sys io import stringio  def decorator_that_makes_func_into_generator(func):     def wrapper(*a, **ka):         # temporarily redirect output stringio instance (intr)         ts, intr = sys.stdout, stringio()         sys.stdout = intr         func(*a, **ka)         # restore normal stdout backup (ts)         sys.stdout = ts         # output intr, split whitespace , use generator         yield intr.getvalue().split()      return wrapper  @decorator_that_makes_func_into_generator def countdown(n):     while n > 0:         print(n)         n = n - 1  print(countdown(5), list(countdown(5))) # <generator object wrapper @ 0x01e09058> ['5', '4', '3', '2', '1'] 

if can change function , if want return countdown (list or other sequence type) , then create generator returned object, decorator'd like

def decorator_that_makes_func_into_generator(func):     def wrapper(*a, **ka):         yield func(*a, **ka)     return wrapper 

note: awesome yield from introduced in python 3.3, on older versions use plain loop instead:

for x in func(*a, **ka):      yield x 

example:

@decorator_that_makes_func_into_generator def countdown(n):     res = []     while n > 0:         res.append(n)         n = n - 1     return res  print(type(countdown(5)), list(countdown(5)))  # output: <class 'generator'> [5, 4, 3, 2, 1] 

nothing stops applying decorator_that_makes_func_into_generator generator:

@decorator_that_makes_func_into_generator def countdown(n):     while n > 0:         yield n         n = n - 1  print(type(countdown(5)), list(countdown(5)))  # outputs <class 'generator'> [5, 4, 3, 2, 1]