I have a section of code with several nested if statements that must be in a certain order. However, one of those ifs is optional. That is, if we do test condition1, we must do it first, but we can skip it if the user prefers. One can do this the following way:

option = True #user can toggle this

if option:
    if condition1:
        if condition2:
            if condition3:
                print("Hello World")
else:
     if condition2:
         if condition3:
            print("Hello World")

However, this reuses a lot of text. What is the best way to do this?

>Solution :

The effect of this:

if condition1:
    if condition2:
        if condition3:
            print("Hello World")

Is the same as:

if condition1 and condition2 and condition3:
    print("Hello World")

Similarly, to replace your entire example:

if option:
    if condition1:
        if condition2:
            if condition3:
                print("Hello World")
else:
     if condition2:
         if condition3:
            print("Hello World")

This makes more sense:

if ((not option) or condition1) and condition2 and condition3:
    print("Hello World")

Since you want the same to happen in either case, which is to print that message.

Have a search for "Python boolean operators" to learn more about how not, and and or work.

Note that the parentheses are technically not required in this case, since and takes precedence over or, and not takes precedence over either – but since you’d have to remember that and there’s no real impact from the parentheses, I figured putting them in and leaving them in makes sense.