How to use the pass statement?

Question

I am in the process of learning Python and I have reached the section about the pass statement. The guide I\'m using defines it as being a Null sta

Answer 1

If you want to import a module, if it exists, and ignore importing it, if that module does not exists, you can use the below code:

try:
    import a_module
except ImportError:
    pass
#rest of your code

If you avoid writing the pass statement and continue writing the rest of your code, a IndentationError would be raised, since the lines after opening the except block are not indented

Answer 2

Suppose you are designing a new class with some methods that you don't want to implement, yet.

class MyClass(object):
    def meth_a(self):
        pass

    def meth_b(self):
        print "I'm meth_b"

If you were to leave out the pass, the code wouldn't run.

You would then get an:

IndentationError: expected an indented block

To summarize, the pass statement does nothing particular, but it can act as a placeholder, as demonstrated here.

Answer 3

You can say that pass means NOP (No Operation) operation. You will get a clear picture after this example :-

C Program

#include<stdio.h>

void main()
{
    int age = 12;

    if( age < 18 )
    {
         printf("You are not adult, so you can't do that task ");
    }
    else if( age >= 18 && age < 60)
    {
        // I will add more code later inside it 
    }
    else
    {
         printf("You are too old to do anything , sorry ");
    }
}

Now how you will write that in Python :-

age = 12

if age < 18:

    print "You are not adult, so you can't do that task"

elif age >= 18 and age < 60:

else:

    print "You are too old to do anything , sorry "

But your code will give error because it required an indented block after elif . Here is the role of pass keyword.

age = 12

if age < 18:

    print "You are not adult, so you can't do that task"

elif age >= 18 and age < 60:

    pass

else:

    print "You are too old to do anything , sorry "

Now I think its clear to you.

Answer 4

as the book said, I only ever use it as a temporary placeholder, ie,

# code that does something to to a variable, var
if var == 2000:
    pass
else:
    var += 1

and then later fill in the scenario where var == 2000

Answer 5

Honestly, I think the official Python docs describe it quite well and provide some examples:

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

>>> while True: ... pass # Busy-wait for keyboard interrupt (Ctrl+C) ...

This is commonly used for creating minimal classes:

>>> class MyEmptyClass: ... pass ...

Another place pass can be used is as a place-holder for a function or conditional body when you are working on new code, allowing you to keep thinking at a more abstract level. The pass is silently ignored:

>>> def initlog(*args): ... pass # Remember to implement this! ...

Answer 6

pass is used to avoid indentation error in python If we take languages like c,c++,java they have braces like

 if(i==0)
 {}
 else
 {//some code}

But in python it used indentation instead of braces so to avoid such errors we use pass. Remembered as you were playing a quiz and

 if(dont_know_the_answer)
      pass

Example program,

  for letter in 'geeksforgeeks':
        pass
  print 'Last Letter :', letter