Using for loops and while loops in Python allows you to automate and efficiently repeat tasks. These loops are fundamental constructs in Python that enable you to iterate over sequences, such as lists, tuples, and strings, or to execute a block of code repeatedly based on a condition.
However, there are scenarios where you need more control over the flow of your loops. For instance, you might encounter a situation where you need to exit a loop prematurely, skip the current iteration, or simply have a placeholder for future code. Python provides three powerful statements to handle these cases: break
, continue
, and pass
.
break
statement allows you to exit a loop entirely when a specific condition is met, effectively stopping the loop execution.continue
statement lets you skip the rest of the code inside the loop for the current iteration and move on to the next iteration.pass
statement is a null operation; it is used as a placeholder in loops, functions, classes, or conditionals where code is syntactically required but you have nothing to execute.Understanding and utilizing these statements can significantly enhance your ability to manage loop control flow, making your code more efficient and easier to read. In the following sections, we will explore practical examples of how to use break
, continue
, and pass
statements in Python loops.
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In Python, the break
statement allows you to exit out of a loop when an external condition is triggered. You’ll put the break
statement within the code block under your loop statement, usually after a conditional if
statement.
Info: To follow along with the example code in this tutorial, open a Python interactive shell on your local system by running the python3
command. Then you can copy, paste, or edit the examples by adding them after the >>>
prompt.
Let’s look at an example that uses the break
statement in a for
loop:
The variable number
is initialized at 0 in this small program. Then a for
statement constructs the loop if the variable number
is less than 10.
Within the for
loop, an if
statement presents the condition that if the variable number
is equivalent to the integer 5, then the loop will break. You can refer to this tutorial on Using for() loop in Python to learn more about using the for
loop.
Note: You can also refer to this tutorial on How to construct while loops in Python to learn more about looping in Python.
Within the loop is also a print()
statement that will execute with each iteration of the for
loop until the loop breaks, since it is after the break
statement.
Let’s place a final print()
statement outside of the for
loop to know when you are out of the loop.
When you run this code, you will get the following output:
This shows that once the integer number
is evaluated as equivalent to 5, the loop breaks, as the program is told to do so with the break
statement.
The break
statement causes a program to break out of a loop.
The continue
statement allows you to skip over the part of a loop where an external condition is triggered, but to go on to complete the rest of the loop. The current iteration of the loop will be disrupted, but the program will return to the top of the loop.
The continue
statement will be within the code block under the loop statement, usually after a conditional if
statement.
Using the same for
loop program as in the break
statement section above, we’ll use a continue
statement rather than a break
statement:
The difference in using the continue
statement rather than a break
statement is that our code will continue despite the disruption when the variable number
is evaluated as equivalent to 5. Let’s review our output:
Here, Number is 5
never occurs in the output, but the loop continues after that point to print lines for the numbers 6–10 before leaving the loop.
You can use the continue
statement to avoid deeply nested conditional code or optimize a loop by eliminating frequently occurring cases you would like to reject.
The continue
statement causes a program to skip certain factors that come up within a loop but then continue through the rest of the loop.
When an external condition is triggered, the pass
statement allows you to handle the condition without the loop being impacted in any way; all of the code will continue to be read unless a break
or other statement occurs.
As with the other statements, the pass
statement will be within the code block under the loop statement, typically after a conditional if
statement.
Using the same code block as above, let’s replace the break
or continue
statement with a pass
statement:
After the if
conditional statement, the pass
statement tells the program to continue running the loop and ignore that the variable number
evaluates as equivalent to 5 during one of its iterations.
You’ll run the program and get the following output:
By using the pass
statement in this program, you notice that the program runs exactly as it would if there were no conditional statements in the program. The pass
statement tells the program to disregard that condition and continue to run the program as usual.
The pass
statement can create minimal classes, or act as a placeholder when working on new code and thinking on an algorithmic level before hammering out details.
The break
, continue
, and pass
statements in Python will allow you to use for
loops and while
loops more effectively in your code.
To work more with break
and pass
statements, you can follow the tutorial How To Create a Twitterbot with Python 3 and the Tweepy Library.
pass
, continue
, and break
in Python?pass
: The pass
statement does nothing; it is used as a placeholder when a statement is syntactically required but no action is needed. For example:continue
: The continue
statement skips the rest of the code in the current iteration and moves to the next iteration of the loop. Example:break
: The break
statement exits the loop immediately, regardless of the iteration condition. Example:break
and continue
statements in a for
loop?The break
statement can be used inside a for
loop to terminate it early when a specific condition is met. Example:
The continue
statement skips the rest of the current iteration and moves to the next iteration. Example:
break
?Once a break
statement is executed, the loop terminates, and the code after the loop is executed. If you want to “continue” a loop after breaking, you need to reinitialize the loop.
For Example:
break
statement in my Python for loops?The break
statement is straightforward to use in a for loop to terminate it when a specific condition is met:
In Python, loops can be written using for
or while
. Examples:
Using a for
loop:
Using a while
loop:
To learn more about using for
loop and while
loop in python, you can refer to the tutorials below:
pass
do in a Python for
loop?The pass
statement acts as a placeholder and performs no action. It’s often used when a block of code is syntactically required but hasn’t been implemented yet:
break
exit all loops ?No, the break
statement only exits the innermost loop where it is executed. To exit nested loops, you can use additional control mechanisms, such as flags or functions. Example:
To exit all loops, you can use a flag or wrap the loops in a function and use return
:
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Well done, Fully understood. Thanks for clarification. Have a nice day
exaplined quite simple, that’s nice; but you have a major error in your code: you modify the counter within the loop. Thr for with range automatically visits all values in the range. If you then increase the counter you will end up having only even numbers printed ;-)
is writing pass necessary? and what if we don’t write it?
pass
: The loop will iterate through numbers 0 to 9. Whennumber
equals5
, thepass
statement is executed, which effectively does nothing, and then the program proceeds to theprint
statement.pass
: The behavior of the program remains unchanged. Theif
statement will do nothing whennumber
is5
, and then the program again proceeds to theprint
statement.Therefore, in this specific case, the
pass
statement is not needed at all. It serves no functional purpose and the code will run exactly the same without it. Theif number == 5:
block could be completely removed unless you plan to add some specific actions whennumber
is5
in the future.Here’s how the code functions without the
pass
statement:This simplified version of the code will output exactly the same results as the version with the
pass
statement. Thepass
is only useful when you have a code block that requires at least one statement but you have nothing to execute. In scenarios where the structure demands a statement (like in an empty function definition, class definition, or part of a conditional statement where no action is required),pass
is used to avoid syntax errors. However, in many practical cases, if the block under a condition like yourif
statement truly requires no operations, the condition might be unnecessary unless it’s a placeholder for future code.let’s consider an example where you’re iterating over a list of task descriptions and you want to execute a block of code only for specific tasks. For other tasks, you might not have decided what to do yet, or they simply require no action. Here,
pass
can be used properly to explicitly indicate that nothing is to be done for certain conditions.Let’s assume you have a list of tasks, and you only want to print out the tasks that are marked as ‘urgent’. For tasks that are ‘optional’, you plan to add handling code later, but for now, you’ll use
pass
.Here’s how the script might look:
Explanation:
tasks
list.pass
statement is used here as a placeholder. This makes it clear to anyone reading the code that you intentionally decided to do nothing for optional tasks at this point. You might also add a comment to indicate future plans for this block.This use of
pass
is proper because it clarifies the intention of the code structure without leaving an empty block, which would result in a syntax error. It is also a clear indicator of a possible future implementation area.Typo in example - blank line between break and print should not be there.
Ok, after searching around, I found some info about blank lines with and without the proper X*4 space indentation.
Short story - when running from command line, a blank line without the proper indentation (blank spaces) gets treated as an end of function.
But, when running the same sequence from a script - that blank line without indentation gets passed along as if it has the indentation (i.e., no error)
More info at: