String Methods

Concept: Strings

A method is an operation you call on a value. Write the value, a dot, the method name and parentheses, as in name.upper(). String methods can change the case of text, replace text or split it into parts.

upper and lower

name = "Sanjin"
print(name.upper())
print(name.lower())

For simple case-insensitive comparisons, lowercasing both strings can make "Red" and "red" match. Only do this when the task asks you to ignore case; some tasks deliberately distinguish uppercase and lowercase.

replace

sentence = "I like cats"
print(sentence.replace("cats", "dogs"))
print(sentence)

Strings cannot be changed in place. Methods such as .upper(), .lower() and .replace() return a string without changing the original. To use the returned text later, save it, for example sentence = sentence.replace("cats", "dogs"). Other string methods can return other types of values.

With two arguments, .replace(old, new) replaces all non-overlapping matches, including matches inside longer words. Matching is case-sensitive. An empty replacement string removes the matching text.

split

With no argument, .split() returns a list of pieces separated by whitespace, such as spaces, tabs or newlines. Repeated whitespace is treated as one separator, and leading or trailing whitespace does not create empty pieces.

line = "red green blue"
words = line.split()
print(words)
print(len(words))

Chaining methods

You can call another method on a result when that result supports the method. Here .lower() returns a string, so .split() can be called on it; .split() then returns a list.

text = "Red RED red"
print(text.lower().split())

text.lower() makes one lowercase string, and .split() turns that into a list — the standard first step for counting words.

See also: Indexing, String Formatting, Lists.

Your turn

Print the title in capitals, then print it with great replaced by small.

title = "the great escape"
# print the title in capitals, then with "great" replaced by "small" (two lines)

Expected output

THE GREAT ESCAPE
the small escape

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