Modify Strings

You can't change a string in place, but you can create modified copies with built-in methods.

Uppercase and lowercase

python
a = "Hello, World!"
print(a.upper())

HELLO, WORLD!
print(a.lower())

hello, world!

Remove whitespace

strip() removes spaces from the start and end:

python
a = "  Hello, World!  "
print(a.strip())

### "Hello, World!"

Replace

replace() swaps one piece of text for another:

python
a = "Hello, World!"
print(a.replace("H", "J"))

Jello, World!

Split

split() breaks a string into a list on a separator:

python
a = "Hello, World!"
print(a.split(","))

### ['Hello', ' World!']

Concatenate (join with +)

python
a = "Hello"
b = "World"
c = a + " " + b
print(c)

### Hello World

Check what's in it

• startswith() and endswith() test the edges.
• find() gives the index of a substring (or -1).
• count() counts occurrences.

python
s = "banana"
print(s.count("a"))

### 3
print(s.find("nan"))

### 2

Strings are immutable

None of these change the original string. They all return a new one.

TL;DR

• upper(), lower(), strip(), replace(), split() return new strings.
• Join strings with + or " ".join(list).
• find(), count(), startswith() inspect text.
• Strings never change in place.