How To Use Break, Continue, and Pass Statements when Working with Loops in Python 3
Table of Contents
Introduction #
Using for loops and while loops in Python allow you to automate and repeat tasks in an efficient manner.
But sometimes, an external factor may influence the way your program runs. When this occurs, you may want your program to exit a loop completely, skip part of a loop before continuing, or ignore that external factor. You can do these actions with break
, continue
, and pass
statements.
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Prerequisites #
You should have Python 3 installed and a programming environment set up on your computer or server. If you don’t have a programming environment set up, you can refer to the installation and setup guides for a local programming environment or for a programming environment on your server appropriate for your operating system (Ubuntu, CentOS, Debian, etc.)
Break Statement #
In Python, the break
statement provides you with the opportunity to exit out of a loop when an external condition is triggered. You’ll put the break
statement within the block of code 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:
number = 0
for number in range(10):
if number == 5:
break # break here
print('Number is ' + str(number))
print('Out of loop')
In this small program, the variable number
is initialized at 0. Then a for
statement constructs the loop as long as the variable number
is less than 10.
Within the for
loop, there is an if
statement that presents the condition that if the variable number
is equivalent to the integer 5, then the loop will break.
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.
To know when we are out of the loop, we have included a final print()
statement outside of the for
loop.
When we run this code, our output will be the following:
Number is 0
Number is 1
Number is 2
Number is 3
Number is 4
Out of loop
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.
Continue Statement #
The continue
statement gives you the option 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. That is, 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 block of code 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:
number = 0
for number in range(10):
if number == 5:
continue # continue here
print('Number is ' + str(number))
print('Out of loop')
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:
Number is 0
Number is 1
Number is 2
Number is 3
Number is 4
Number is 6
Number is 7
Number is 8
Number is 9
Out of loop
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 to optimize a loop by eliminating frequently occurring cases that 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.
Pass Statement #
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 block of code 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:
number = 0
for number in range(10):
if number == 5:
pass # pass here
print('Number is ' + str(number))
print('Out of loop')
The pass
statement occurring after the if
conditional statement is telling the program to continue to run the loop and ignore the fact that the variable number
evaluates as equivalent to 5 during one of its iterations.
We’ll run the program and consider the output:
Number is 0
Number is 1
Number is 2
Number is 3
Number is 4
Number is 5
Number is 6
Number is 7
Number is 8
Number is 9
Out of loop
By using the pass
statement in this program, we notice that the program runs exactly as it would if there were no conditional statement 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.
Conclusion #
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 our project tutorial “How To Create a Twitterbot with Python 3 and the Tweepy Library.”