Python comes with dozens of built-in functions — no import needed. They help you transform, measure, or convert values in one line of code.

In this chapter, weєll group these functions by purpose — numbers, text, types, and collections.

Converting Data Types

These functions let you convert between basic types:

• int() — to integer;
• float() — to float;
• str() — to string;
• bool() — to Boolean.

Useful when working with input, formatting, or expressions.

Working with Numbers

These help clean or adjust numeric values:

• abs() — absolute value (removes minus sign);
• round() — rounds floats to nearest whole or to decimals.

Working with Strings

These are commonly used for cleaning and formatting text:

• lower() — make all letters lowercase;
• upper() — make all letters uppercase;
• strip() — remove spaces at the beginning and end;
• replace() — replace part of a string with another;
• split() — turn a string into a list of words;
• join() — combine list items into one string.

Collection Inspection

These return information about a list, tuple, or other iterable:

• len() — count items;
• max() — largest value;
• min() — smallest value;
• sum() — total of all numbers.

Collection Transformation

These are helpful when looping, combining, or transforming collections:

• sorted() — returns sorted list;
• enumerate() — adds index numbers;
• zip() — pairs items from multiple lists;
• range() — creates a sequence of numbers;
• map() — applies a function to each item;
• filter() — keeps items that meet a condition.

Summary

• Python's built-in functions save you time and code;
• You can convert data, adjust text, transform collections, and get answers instantly;
• These tools become essential as you build more complex programs.

Try It Yourself

1. Convert the string "42" to an integer using int(), and then to a float using float();
2. Use abs() and round() on the number -5.8 to clean and format it;
3. Take the string " Hello, World! " and apply strip(), lower(), and replace() to tidy and modify it;
4. Create a list of numbers: [3, 7, 2, 9]. Use len(), max(), and sum() to inspect it;
5. Use enumerate() to loop over the list and print both index and value. Then use map() to double each item.