16.8. For Each Item Loop

Because it is very common to use a for loop to touch each of the elements of a collection, we can do it without even using a range and index. We can use a for loop that repeats the body of the loop one time for each value in the collection. This is sometimes called a for each loop since it repeats the body of the loop one time for each element in the collection. It works for both strings and lists as shown below.

# initialize the list myList = [0,1,2,3,"end"] # loop through the items in the list for item in myList: # print the current item print(item) # initialize the string myString = "MLK" # loop through the characters in the string for character in myString: # print the current character print(character)

This isn’t actually a different for loop. The function range actually creates a list of numbers, and the index just steps through each of those items one at a time.

# initialize the variables myString = "MLK" myList = range(0,len(myString)) # loop through the indices in myList and print each character for index in myList: print(myString[index])

What would happen if we changed line 2 to myList = range(0,len(myString)/2)? (Hint: You could try it)

• We would get an error for doing math in a range function.
• You are allowed to do math in a range function.
• We would get an error because len(myString)/2 is 1.5 which can't be used in a range.
• Dividing 3 by 2 results in 1.5, which can't be used in a range.
• We would get "M L K" printed with one character per line.
• This would be true if dividing by 2 was truncated to 1.
• We would get "M L K " printed with one character per line plus an extra space at the end.
• This would be true if 1.5 was rounded to 2, but that doesn't happen.

Note

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