The pass keyword in Python is a placeholder statement that indicates that a certain block of code intentionally does nothing. Since the Python syntax requires that code blocks must have at least one statement, the pass statement allows you to write a block without actually specifying any code.
The pass keyword is essentially meaningless by itself, except for the purposes of satisfying Python’s syntax requirements.
The pass keyword can be used in multiple contexts in your code, and you can use it for a number of reasons.
1. A Placeholder in Functions, Conditional Statements, and Loops
When defining functions, conditional statements, and loops, you may not have the actual code for the function or loop body at the outset. In such cases, you may choose to use the pass keyword in those code blocks. This allows you to write and test your code without worrying about what each individual block of code does yet.
Using pass in a Function
def func(): pass func()
The output of the above code does nothing, as it is a plain function call
Using pass in If Statement
if 1<2: pass else: print("No")
In the above code, the pass keyword is used in the code block for the if statement when 1<2. The output is that there is ‘No’ output.
Using pass in While Loop
i=1 while i<6: if i == 3: pass else: print(i) i+=1
In the above code, the pass keyword is used in the code block for the if statement when i==3, allowing the loop to do nothing for that iteration. The output of the loop is:
2. Placeholder for Future Code Substitution
The pass keyword can also be useful as a placeholder for future code replacement. In this use case, you can write the “skeleton” of your code and use the pass keyword as a placeholder for where additional functionality needs to be added later.
for n in [1, 2, 3, 4, 5]: if n%2==0: pass else: print("This is Odd Number: ", n)
In the code above, the pass keyword is used in the code block for the if statement when n%2==0, allowing the loop to do nothing for even numbers. The output of the loop is:
This is Odd Number: 1
This is Odd Number: 3
This is Odd Number: 5
3. Signaling that You are Yet to Finish your Code Block
Another use of the pass keyword is as a placeholder until you decide what code should actually be in a certain code block. If you use the pass keyword in the code block, it indicates to other programmers (and yourself) that this is a section of code that you are not finished with yet, and will come back and finish later.
def func(a): if len(a)>=4: pass else: print("Please enter maximum 4 characters") b='apple' func(b)
In the code above, if the length of the string is greater than or equal to 4, the function code block does nothing, but doesn’t complain, as the length of the string is greater than or equal to the required length of 4.
Please enter maximum 4 characters
The pass keyword in Python is a simple but useful feature of the language that allows you to signify where code blocks exist without writing anything in the block. The pass statement serves both to satisfy Python’s syntax requirements and to help other programmers and yourself understand that these are areas of code where you need to come back and add more functionality later.