Python pass statement Explained [Beginners Guide]

What does pass do in Python?

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

If you use a Python statement that expects a sub-block of code or suite, and one is not present, you will get a syntax error condition. For this reason, we have pass, a statement that does absolutely nothing—it is a true NOP, to steal the “No OPeration” assembly code jargon. Style- and development-wise, pass is also useful in places where your code will eventually go, but has not been written yet

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Another use of pass statement is as a place-holder for a function or conditional body when we are working on new code, so as to allow the developer keep thinking at a more abstract level. The pass can also be used to create minimal classes. Hence, it can also be considered as a null statement. Hence, pass statement helps avoiding the error when empty code is not allowed.

The pass statement is widely used as a place-holder. When used with a condition, it behaves like a continue statement. The syntax of pass statement when used with looping or a class is as shown below.

 

Some practical examples

Example 1 - Using pass in while loop

The example here iterates over the range of numbers from 1 to 10 and executes pass as the developer does not know what to code inside the while loop. Hence, pass act as a placeholder.

# Initializing
i=1

# Iterating while loop
while i <= 10:
    # Developer doesn't know what to code inside the loop and so uses <code>pass as a place-holder pass i+=1 else: print("Ending of while loop") 

Output

Ending of while loop

 

Example 2 - Using pass while iterating over a list

When you want to iterate over the sequence one way is to iterate using the for loop given below that gives the position of the desired element. Here, we are performing linear search to search the element whose value is "China". The example below iterates over a Python list containing names of countries and skips the "China" while printing the other countries. Hence, it behaves like a continue statement.

# Initializing
l1=['India','Nepal','Srilanka','China','Australia']
for country in l1:
	if country == 'China':
		pass
	else:	
		print (country)

Output

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India
Nepal
Srilanka
Australia

 

Example 3 - Using pass statement with an empty function

In the example given below, we are writing a display function in Python containing only pass statement as a place-holder. When we call this function, no action will be taken. Hence, it provides the developer a flexibility to structure the application and add the functionalities step by step.

# Initializing
def display():
	pass
a=10
b=20
display()
print("value of a is "a, "and b is",b)

Output

value of a is 10 and b is 20

 

Example 4 - Using pass statement used with empty class

In the example given below, we are writing an empty python class. Python doesn't allow the empty class, but if we are not sure about the implementation of the class we can simply write pass statement as a place-holder so as to add the implementation later during the development.

class employee:
	pass

 

Summary

The knowledge of control flow statement pass is core to python programming language that is very useful to formulate a complex logic easily and define the structure of the program before going for actual implementation. You will frequently need to use the pass statements as a place holder to build varied of applications. The knowledge of pass in different scenarios and combinations helps solving the really complex task to a time efficient solution. Hence, pass statement helps avoiding the error when empty code is not allowed.

In this tutorial, we covered the pass statement with for loop, while loop, empty function, empty class along with the difference between pass and other control flow statements like break, continue and return with an example to demonstrate the functionalities of pass statement. All in all, this tutorial, covers everything that you need to know in order to understand and use the pass statement in Python.

 

References

Control Flow statement

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