String methods

Strings come with built-in tools called methods, used with a dot:

s = "  hello WORLD  "
s.strip()        # "hello WORLD"   trim spaces
s.lower()        # "  hello world  "
s.title()        # "  Hello World  "
s.upper()        # "  HELLO WORLD  "
s.replace("l", "L")
"a,b,c".split(",")   # ["a", "b", "c"]

String methods do not change the original string: strings are immutable. Methods such as .strip() return a new string, so store the result. Methods can also be chained: s.strip().title().

s.split() with no argument splits on whitespace and returns a list of words. Lists use indexes just like strings: words[0] is the first item and words[1] the second. len(words) counts the items.

See it run

tag = " ruby "
tag.upper()
shout = tag.upper()
tag = tag.strip()

Strings never change in place. Watch what tag holds after each line.

Practice string methods

Exercise 1

From messy = " hello WORLD " make:

clean = "Hello World" (strip + title)
shout = clean in upper case
words = clean split into a list of words

Exercise 2

People type email addresses sloppily. From raw in the code editor below, make:

email = raw with the spaces trimmed and in lower case ("ada.lovelace@example.com")
parts = email split at the @
username = the first item of parts, domain = the second

Exercise 3

A blog turns post titles into web addresses called slugs. From title in the code editor below, make:

slug = trimmed, lower case, with every space replaced by - ("my-first-python-blog-post")
word_count = how many words the title has (5)

The check will try a different title too, so build both from title.

Free lesson: use the editor to practice it.

Practice

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Visualizer Watch your code run line by line

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Memory · names → values

Variables appear here as Python creates them.

Output & plots