8.5 Splitting/joining strings

Learning objectives

By the end of this section you should be able to

Use the split method to split a string into substrings.
Combine objects in a list into a string using join method.

split

A string in Python can be broken into substrings given a delimiter. A delimiter is also referred to as a separator. The split method, when applied to a string, splits the string into substrings by using the given argument as a delimiter. Ex: "1-2".split('-') returns a list of substrings ["1", "2"]. When no arguments are given to the split method, blank space characters are used as delimiters. Ex: "1\t2\n3 4".split returns ["1", "2", "3", "4"].

join

The join method is the inverse of the split method: a list of string values are concatenated together to form one output string. When joining string elements in the list, the delimiter is added in-between elements. Ex: ','.join(["this", "is", "great"]) returns "this,is,great".

Try It

Unique and comma-separated words

Write a program that accepts a comma-separated sequence of words as input, and prints words in separate lines. Ex: Given the string "happy,smiling,face", the output would be:


    happy
    smiling
    face

s = "happy,smiling,face"

Try It

Lunch order

Use the join method to repeat back a user's order at a restaurant, separated by commas. The user will input each food item on a separate line. When finished ordering, the user will enter a blank line. The output depends on how many items the user orders:

If the user inputs nothing, the program outputs:
You ordered nothing.
If the user inputs one item (Ex: eggs), the program outputs:
You ordered eggs.
If the user inputs two items (Ex: eggs, ham), the program outputs:
You ordered eggs and ham.
If the user inputs three or more items (Ex: eggs, ham, toast), the program outputs:
You ordered eggs, ham, and toast.

In the general case with three or more items, each item should be separated by a comma and a space. The word "and" should be added before the last item.

# Keep reading/storing input until a blank line.
food = []
while True:
    line = input()
    if line == "":
        break
    food.append(line)

# Repeat back the order, separated by commas.
if len(food) == 0:
    print("You ordered nothing")

Adapted from Introduction to Python Programming by OpenStax (openstax.org), licensed under CC BY-NC-SA 4.0. Changes were made. License: CC-BY-NC-SA-4.0.