pass Statement in Python
As name suggests, the pass statement does nothing, as it gets treated as a null statement. Now may be, this question may arise in your mind:
- If pass statement does nothing, then why we need/use it or why Python provides this statement ?
The answer to this question may be according to the programmer's need. But I've provided two solid reasons/answers for the above question, that are:
- We can use pass statement wherever the statement is required to avoid syntax error. And only if that section of program does not require to take any action.
- We can also use pass statement, if we want to add some block of codes in future. That is, in short, pass statement can also be worked as a placeholder for whatever the block of code, we want to write in future
Important - The pass statement does nothing, it is only required when syntactically needed to avoid syntax error, but actually to do nothing. That is, if the program's need to provide the statement, but we want to do nothing, then we can use pass keyword or statement there.
Syntax of pass Statement
The complete statement of pass is nothing, but the pass keyword itself, therefore if we talk about its syntax, then it is just the keyword pass like shown below:
We can use pass statement, wherever we want in the whole Python program such as:
- We can use it in conditional block
- We can use it in user-defined function
- We can also use it in classes
Examples of pass Statement
The theory part of the pass statement is completed. Therefore it's time to take its examples. Example helps a lot to understand the topic in computer programming world like Python:
nums = [1, 2, 3, 4, 5] for n in nums: if n==2: pass else: print(n)
The snapshot given below shows the sample output produced by above example program on pass statement:
As you can see from the above sample output, the number 2 gets skipped to print. Because using the if statement, I've applied the condition n==2, that tells, whenever the value of n becomes equal to 2, then program flow goes inside the body of if. And inside the body of if, I've used the pass statement, that does nothing.
Since the pass statement does nothing, it just passes that block or body where it is present. Let's take another example, relatable to previous program:
nums = [1, 2, 3, 4, 5] for n in nums: if n==2: pass print(n)
This time, the program produces all the five numbers on output like shown in the snapshot given below:
Unlike continue that forces the loop to continue for its next iteration, skipping rest statement(s), that lies below the continue keyword in the same indentation, to execute. Confused ? Let's take an example to differentiate between these two :)
nums = [1, 2, 3, 4, 5] for n in nums: if n==2: continue print(n)
This program produces following output:
Either pass works as a placeholder for future code or used to avoid syntax error. For example, the following program:
nums = [1, 2, 3, 4, 5] for n in nums: if n == 3: print(n)
Produces an error like shown in the snapshot given below:
Therefore, to avoid these types of syntax error, we use pass statement like shown in the program given below:
nums = [1, 2, 3, 4, 5] for n in nums: if n == 3: pass print(n)
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