Generators and Decorators

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Generator creates the value on the fly.

# Generators help you make lazy code
def double_numbers(iterable):
    for i in iterable:
        yield i + i

# Instead of generating and returning all values at once it creates one in each iteration
# so values bigger than 15 wont be processed in double_numbers
# note range is a generator too, creating a list 1-900000000 would take lot of time
_range = range(1, 900000000)
# will double all numbers until a result >=30 found
for i in double_numbers(_range):
    if i >= 30:


in this example beg wraps say. beg will call say. If say_please is True then it will change the returned message.

from functools import wraps

def beg(_say):
    def wrapper(*args, **kwargs):
        msg, say_please = _say(*args, **kwargs)
        if say_please:
            return "{} {}".format(msg, "Please! I am poor :(")
        return msg
    return wrapper

def say(say_please=False):
    msg = "Can you buy me a beer?"
    return msg, say_please

print(say())  # Can you buy me a beer?
print(say(say_please=True))  # Can you buy me a beer? Please! I am poor :(
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