How do I get a python program to do nothing?

How do I get a Python program to do nothing with if statement?

 if (num2 == num5): #No changes are made 

5 Answers

You could use a pass statement:

if condition: pass 

Python 2.x documentation

Python 3.x documentation

However I doubt you want to do this, unless you just need to put something in as a placeholder until you come back and write the actual code for the if statement.

If you have something like this:

if condition: # condition in your case being `num2 == num5` pass else: do_something() 

You can in general change it to this:

if not condition: do_something() 

But in this specific case you could (and should) do this:

if num2 != num5: # != is the not-equal-to operator do_something() 

The pass command is what you are looking for. Use pass for any construct that you want to "ignore". Your example uses a conditional expression but you can do the same for almost anything.

For your specific use case, perhaps you'd want to test the opposite condition and only perform an action if the condition is false:

if num2 != num5: make_some_changes() 

This will be the same as this:

if num2 == num5: pass else: make_some_changes() 

That way you won't even have to use pass and you'll also be closer to adhering to the "Flatter is better than nested" convention in PEP20.

You can read more about the pass statement in the documentation:

The pass statement does nothing. It can be used when a statement is required syntactically but the program requires no action.

if condition: pass 

try: make_some_changes() except Exception: pass # do nothing 

class Foo(): pass # an empty class definition 

def bar(): pass # an empty function definition 

you can use pass inside if statement.

if (num2 == num5): for i in []: #do nothing do = None else: do = True 

or my personal favorite

if (num2 == num5): while False: #do nothing do = None else: do = True 

You can use continue

if condition: continue else: #do something