Modules

Modules

• A Python program may consist of multiple modules (.py files) of code
• Modules may import other modules
• Multiple files embedded into one another
• Forming one large program

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Where does a Python program start?

Where does a Python program start?

• In most languages, a program always starts with a function called main
• If you execute/run a Python file/module, it will start at the first executable statement
• The first unindented executable statement
• Function definitions are not executable

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• Many Python programmers set up a main function like this

def main():

print("Hello World!")

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if __name__ == "__main__":

main()

https://realpython.com/python-main-function/

if __name__ == "__main__":

• This block distinguishes between whether the module has been executed directly ( __name__ == "__main__" is True), or imported
• If a module has executable code out of the special block
• That code will be run even if the module is imported

print("Hello from find_functions")

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def find_first(values, x):

return values.index(x)

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if __name__ == "__main__":

print(find_first([1, 2, 3, 1, 2, 3, 1, 2, 3], 2))

Importing code from other modules - 1

• import module_name

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• Example from test1.py:

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import find_functions

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print("Hello from test1")

ml = [6, 7, 6, 7, 6, 7]

x = find_functions.find_first(ml, 6)

print(find_functions.MAX)

Importing code from other modules - 2

• from module_name import item_name

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• Example from test2.py:

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from find_functions import find_last

from find_functions import MAX

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print("Hello from test2")

ml = [6, 7, 6, 7, 6, 7]

x = find_last(ml, 6)

print(x, MAX)

Importing code from other modules - 3

• from module_name import function_name as alias

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• Example from test3.py:

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import find_functions as ff

from find_functions import MAX as SIXTEENCUBED

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print("Hello from test3")

ml = [6, 7, 6, 7, 6, 7]

x = ff.find_middle(ml, 6)

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print(x, SIXTEENCUBED)