A loop can contain one or more other loops: you can create a loop inside a loop. This principle is known as nested loops. Nested loops go over two or more loops.
Programmers typically nest 2 or 3 levels deep. Anything higher than that is just confusing.
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Example
Lets do a simple example. We create two lists:
persons = [ "John", "Marissa", "Pete", "Dayton" ]
restaurants = [ "Japanese", "American", "Mexican", "French" ]
If we have a list of persons who like to eat at restaurants, can we make every one of them eat a certain restaurant?
#!/usr/bin/python
persons = [ "John", "Marissa", "Pete", "Dayton" ]
restaurants = [ "Japanese", "American", "Mexican", "French" ]
for person in persons:
for restaurant in restaurants:
print(person + " eats " + restaurant)
This goes over both loops:
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Exercises
Try the exercises below
-
Given a tic-tac-toe board of 3x3, print every position
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Create a program where every person meets the other persons = [ "John", "Marissa", "Pete", "Dayton" ]
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If a normal for loop finishes in n steps O(n), how many steps has a nested loop?
After completing these continue with the next exercise.