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LearnPython/AdvancedTutorials/11_Closures.py
2024-09-19 12:43:22 +02:00

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Python

# A Closure is a function object that remembers values in enclosing scopes even if they are not present in memory. Let us get to it step by step
# Firstly, a Nested Function is a function defined inside another function. It's very important to note that the nested functions can access the variables of the enclosing scope. However, at least in python, they are only readonly. However, one can use the "nonlocal" keyword explicitly with these variables in order to modify them.
def transmit_to_space(message):
"This is the enclosing function"
def data_transmitter():
"The nested function"
print(message)
data_transmitter()
print(transmit_to_space("Test message"))
# This works well as the 'data_transmitter' function can access the 'message'. To demonstrate the use of the "nonlocal" keyword, consider this
def print_msg(number):
def printer():
"Here we are using the nonlocal keyword"
nonlocal number
number=3
print(number)
printer()
print(number)
print_msg(9)
# Without the nonlocal keyword, the output would be "3 9", however, with its usage, we get "3 3", that is the value of the "number" variable gets modified.
# Now, how about we return the function object rather than calling the nested function within. (Remember that even functions are objects. (It's Python.))
def transmit_to_space(message):
"This is the enclosing function"
def data_transmitter():
"The nested function"
print(message)
return data_transmitter
fun2 = transmit_to_space("Burn the Sun!")
fun2()
# Exercise
# Make a nested loop and a python closure to make functions to get multiple multiplication functions using closures. That is using closures, one could make functions to create multiply_with_5() or multiply_with_4() functions using closures.
def multiplier_of(n):
def multiplier(number):
print("n:",n)
print("number:", number)
return number*n
return multiplier
multiplywith5 = multiplier_of(5)
print(multiplywith5(9))