REFERENCEpython

python Documentation

📖 INDEX

# print

# arithmetic-operators

# assignment-operators

# comparison-operators

# logical-operators

# identity-operators

# membership-operators

# keyword-arguments-kwargs

# default-parameter-value

# class-methods-classmethod

# static-methods-staticmethod

# dunder-methods

# try-block

# except-block

# else-block-exceptions

# list-comprehensions

# dictionary-comprehensions

# set-comprehensions

# iterators

# property-decorator-property

# context-managers-contextmanager

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Strings

AI & DATA SCIENCE // strings

A string (str) is Python's built-in, immutable type for representing text as a sequence of Unicode characters.

Syntax

s = 'hello'
s = "hello"
s = '''multi\nline'''
f"{value}"

Deep Dive Course

Strings in Python 3 are sequences of Unicode code points, immutable like tuples, meaning every 'modification', like .upper() or concatenation, actually returns a brand-new string rather than changing the original in place. They support indexing, slicing, iteration, and a large set of built-in methods for searching, splitting, and formatting, with f-strings (introduced in Python 3.6) now the standard way to interpolate values.

1Understanding Strings

💡

Because strings are immutable, repeatedly concatenating one inside a loop with += rebuilds the whole string each time — for building up large text, collect pieces in a list and join them once at the end instead.

editor.html

name = "world"
greeting = f"Hello, {name}!"
print(greeting)
print(greeting.upper())

localhost:3000

2Practical Example

Here is a real-world application of Strings showing how it is used in production Python code.

editor.html

words = ["Python", "is", "fun"]
sentence = " ".join(words)
print(sentence)
print(sentence[:6])

localhost:3000

3Best Practices

Follow these guidelines when working with Strings:

1. Use f-strings for formatting instead of % formatting or .format(), for readability and slightly better performance

2. Use ''.join(pieces) instead of += in a loop when building a large string from many parts

3. Use triple-quoted strings for multi-line text or docstrings instead of manual newline concatenation

⚠️

Tip: Because strings are immutable, repeatedly concatenating one inside a loop with += rebuilds the whole string each time — for building up large text, collect pieces in a list and join them once at the end instead.

editor.html

name = "world"
greeting = f"Hello, {name}!"
print(greeting)
print(greeting.upper())

localhost:3000

Examples

Example 01Basic Usage

name = "world"
greeting = f"Hello, {name}!"
print(greeting)
print(greeting.upper())

Example 02Advanced Example

words = ["Python", "is", "fun"]
sentence = " ".join(words)
print(sentence)
print(sentence[:6])

Best Practices

Use f-strings for formatting instead of % formatting or .format(), for readability and slightly better performance
Use ''.join(pieces) instead of += in a loop when building a large string from many parts
Use triple-quoted strings for multi-line text or docstrings instead of manual newline concatenation

Interview Question

Why is it inefficient to build a large string by repeatedly using += inside a loop?▼

Hint: Think about what immutability means for each concatenation.

Since strings are immutable, every += creates an entirely new string object containing the old content plus the new piece, copying all the previously accumulated characters each time. Over many iterations this becomes quadratic time overall. Collecting the pieces in a list and calling ''.join() once at the end does the concatenation in a single linear pass instead.

Exercises

MediumPractice using Strings in a real scenario.

View Solution

name = "world"
greeting = f"Hello, {name}!"
print(greeting)
print(greeting.upper())

Frequently Asked Questions

Why is it inefficient to build a large string by repeatedly using += inside a loop?▼

Related Functions

f-stringslist()bytes