6.1. for loops

A loop is initialized with the keywords for and in. In the first line, you must create a loop variable (the variable that changes each loop iteration) and the iterable object to loop through. This line must end with a colon. Subsequent code must be indented with 4 spaces. The loop variable can be named anything. The iterable object must be an existing object.

The first line of a for loop should look like:

COPYpython
1for loop_variable in interable_object:

Below are syntax examples of how to loop over common data structures.

6.1.1 Looping over list elements

COPYpython
1# Syntax
2for element in list_object:
3    # <code applied to each element in list_object>

In each iteration, element will equal an item in list_object.

6.1.2 Looping over indices

COPYpython
1# Syntax
2for i in range(0,11):
3    # <code applied in each iteration>

In each iteration, i will equal a number 0 to 10. You can use i to index a list or nested list.

6.1.3. Looping over dictionaries

COPYpython
1# Syntax
2for key_name, dict_value in dict_object.items():
3    # <code applied to each list in dict_object>

key_name and dict_value are both loop variables equal to the key and value of the dictionary, respectively. items() is a dictionary object method needed to make the loop work.