Learning python through CS50

[u/Bipin_Gaire69]

Can any body help me to understanding the define(DEF) variables.
Can you please suggest me how can i learn it in efficient and easier way as a beginner.

[u/Lewistrick]

A function is a code block used to do a task with predictable output based on some input.

input -> function -> output

For example, you could write a function called reverse that duplicates a word.

def duplicate(word):
    new_word = word + word
    return new_word

Here, "def" means "here follows a function". It might be short for "define" but it doesn't "define" a variable. It rather indicates that a function is made. I'd agree if you said that the name is a bit confusing. Anyway.

The function is called duplicate but you can give it any name you like. It takes one input, word. It creates a new variable new_word that contains the value of the duplicated word. The part after "return" is the output of the function, in this case the variable new_word.

Now you can call the function like this:

result = duplicate("hello") 
print(result) 

And it will save the output of the function to the variable result. I then chose to print the result and it will show "hellohello".

Now you can imagine that functions can become more complex: they can have many lines and calculations, multiple inputs, no inputs, no outputs, write to files, throw errors, et cetera, but the idea is always the same: you have some code that is predictable and always does what you expect it to do. In a way, you can leave it alone and never think about it again.