Programming Fundamentals › Programming Basics

String

A sequence of characters, usually immutable.

Also known as: text, str, string literal

A string is a sequence of characters: text. You write it in quotes.

name = "Ana"
len(name)                    # 3
name.upper()                 # "ANA"
name + " Putri"              # "Ana Putri"   concatenation
name[0]                      # "A"           indexing
name[1:]                     # "na"          slicing
"na" in name                 # True
"a,b,c".split(",")           # ["a", "b", "c"]
" hi ".strip()               # "hi"

Strings are immutable

In Python, JavaScript, Java and many others, you can’t change a string in place. Methods return a new string:

name.upper()       # returns "ANA"; name is still "Ana"
name = name.upper()

Building a long string by repeated + in a loop is slow in some languages. Collect pieces in a list and join them: "".join(parts).

Things that trip people up

• A string isn’t a number. "42" + 1 fails or gives "421". Convert first (type conversion).
• Length isn’t always what you see. Emoji and accented characters can be several code points (Unicode), so len may surprise you.
• Encoding matters when text becomes bytes (character encoding).
• Quotes inside strings need escaping ("say \"hi\"") or different quote types.
• Comparison is case-sensitive, and sort order follows character codes unless you ask for locale rules.
• Never build SQL or HTML by concatenating user input. That’s how injection happens (SQL injection).

To insert values into text, use interpolation rather than +.