The Python continue Statement

Introduction

The Python continue statement allows you to skip the rest of the current iteration and resume executing the code from the next one. It is conceptually very similar to the break statement, which exits the loop entirely. While the break statement is used to exit a loop, the continue statement will just skip the rest of the current iteration and pick up with the following one. Like break, continue can be used with both for and while loops.

Basic continue Statement Syntax

To skip the rest of the code in an iteration of a loop, just write the keyword continue on its own line. To skip the rest of the code in an iteration of a loop, just write the keyword continue on its own line. It must be placed within a loop, otherwise a `continue` will cause a syntax error.

continue should be used with a conditional statement since not doing so will result in useless, unreachable code following it.

Here’s the basic syntax for the continue statement with a for loop:

for element in iterable:
    # code above 
    if condition:
        continue
    # code below

And here’s the basic syntax for continue with a while loop:

while loop_condition:
    # code above 
    if condition:
        continue
    # code below

Using continue with for Loops

for loops iterate through all items in an iterable, and the continue statement is useful when you want to skip executing some code for certain items based on a condition.

Example:

dogs = ["Scooby-Doo", "Snoopy", "Goofy", "Clifford", "Astro"]
sick_dogs = ["Snoopy", "Clifford"]

for dog in dogs:
    print(f"{dog}'s activities: ")
    print(f"   Gets a treat.")
    
    if dog in sick_dogs:
        continue
        
    print(f"   Plays fetch.")
    print(f"   Goes running in the yard.")

Output:

Scooby-Doo's activities: 
   Gets a treat.
   Plays fetch.
   Goes running in the yard.
Snoopy's activities: 
   Gets a treat.
Goofy's activities: 
   Gets a treat.
   Plays fetch.
   Goes running in the yard.
Clifford's activities: 
   Gets a treat.
Astro's activities: 
   Gets a treat.
   Plays fetch.
   Goes running in the yard.

The purpose of the code in the example above is to list a day’s activities for some dogs. Every dog gets a treat, but dogs that are sick and who need rest, skip the physical activities of playing fetch and running in the yard.

It works by iterating though the dogs array with the for loop on line 4. The sick dogs are given by the sick_dogs array (Snoopy and Clifford), and lines 8 and 9 skip the physical activities for those using a continue statement.

Using continue With while Loops

The continue statement can also be used from within while loops. Here is the example above, re-written with a while loop:

Example:

dogs = ["Scooby-Doo", "Snoopy", "Goofy", "Clifford", "Astro"]
sick_dogs = ["Snoopy", "Clifford"]

i = 0
while i < len(dogs):
    dog = dogs[i]
    i += 1
    
    print(f"{dog}'s activities: ")
    print(f"   Gets a treat.")
    
    if dog in sick_dogs:
        continue
        
    print(f"   Plays fetch.")
    print(f"   Goes running in the yard.")

Output:

Scooby-Doo's activities: 
   Gets a treat.
   Plays fetch.
   Goes running in the yard.
Snoopy's activities: 
   Gets a treat.
Goofy's activities: 
   Gets a treat.
   Plays fetch.
   Goes running in the yard.
Clifford's activities: 
   Gets a treat.
Astro's activities: 
   Gets a treat.
   Plays fetch.
   Goes running in the yard.

The example above is the same as the prior example, except that it uses a while loop. By using a while loop, we have to add some indexing code that the for loop does for us behind the scenes.

The program initializes the index i on line 4, and then accesses a dog item from the array on line 6. The value of the index is incremented on line 7 in order to fetch the next dog on the next iteration. In this case, we must be sure to increment i before the continue block on lines 12 and 13. Otherwise, it won’t be incremented for the first sick dog, and the program will get stuck in an infinite loop.

Understanding Python continue Behavior in Nested Loops

Similar to the break statement, the continue statement only affects the innermost loop where it is located when used within nested loops.

Example:

for i in range(3):
    for j in range(3):
        if j == i:
            continue
        print(f"({i}, {j})")

Output:

(0, 1)
(0, 2)
(1, 0)
(1, 2)
(2, 0)
(2, 1)

The above example prints all pairs of integers from 0 to 2, but skips the ones that have two of the same number. It does this by using two nested for loops on lines 1 and 2. It then tests whether the numbers are equal on line 3, and if so, skips the print statement (line 5) with the continue on line 4. The continue only exits the iteration of the innermost loop (the for on line 2).

Using an if Statement as an Alternative to continue

An alternative to the continue statement involves employing an if statement to achieve similar code execution logic. By strategically placing the if statement within the loop structure, specific code blocks can be conditionally executed or skipped based on the desired criteria.

This alternative approach enhances code readability, making it easier to identify conditions influencing the execution of specific code segments. The decision between using an if statement or the continue statement often comes down to personal stylistic preferences, with both options offering effective ways to control loop flow.

Example:

dogs = ["Scooby-Doo", "Snoopy", "Goofy", "Clifford", "Astro"]
sick_dogs = ["Snoopy", "Clifford"]

for dog in dogs:
    print(f"{dog}'s activities: ")
    print(f"   Gets a treat.")
    
    if dog not in sick_dogs:
        print(f"   Plays fetch.")
        print(f"   Goes running in the yard.")

The example above performs the same logic as the first example and results in the same output. However, instead of using a continue to skip physical activities for the sick dogs, it uses the if statement on line 8.

The if dog in sick_dogs: conditional (line 8) in the original code becomes if dog not in sick_dogs: with the addition of the not operator. The original code skipped physical activity if a dog is sick, whereas now this code permits the physical activity (performed by the indented code on lines 9 and 10) if the dog is not sick.

Summary & Reference for the Python continue Statement

The Python continue statement provides a way to skip the rest of the current iteration within loops, allowing the code to resume with the next iteration. Similar to the break statement, continue is often employed within conditional statements to selectively execute code based on specific conditions.

To apply the continue statement, place it on its own line within a loop, typically within an if statement that checks a particular condition.

Here is an example of using continue from within a for loop:

for dog in dogs:
    # Some code
    if dog in sick_dogs:
        continue
    # Code for activities of non-sick dogs

Here is an example of using continue from within a while loop:

i = 0
while i < len(dogs):
    # Some code
    if dogs[i] in sick_dogs:
        i += 1
        continue
    # Code for activities of non-sick dogs

An if statement can be used as an alternative to continue to allow the same execution logic and enhance readability.

When used within nested loops, the continue statement affects only the innermost loop where it is located.