Python Built-in Functions

Python has a rich set of built-in functions that perform various tasks such as mathematical operations, data manipulation, type conversions, input/output, and more. These functions are always available in the Python environment, meaning you don’t need to import any libraries to use them.

Here’s an overview of commonly used Python built-in functions, grouped by category:

1. Mathematical Functions

• abs(x): Returns the absolute value of a number.

  abs(-5)  # Output: 5
  

• pow(x, y): Returns x raised to the power y.

  pow(2, 3)  # Output: 8
  

• round(x, n): Rounds a number x to n decimal places.

  round(3.14159, 2)  # Output: 3.14
  

• min(*args) / max(*args): Returns the smallest or largest value from a set of values.

  min(1, 2, 3)  # Output: 1
  max(1, 2, 3)  # Output: 3
  

• sum(iterable): Returns the sum of all items in an iterable.

  sum([1, 2, 3])  # Output: 6
  

2. Type Conversion Functions

• int(x): Converts x to an integer.

  int("10")  # Output: 10
  

• float(x): Converts x to a float.

  float("10.5")  # Output: 10.5
  

• str(x): Converts x to a string.

  str(10)  # Output: "10"
  

• list(iterable): Converts an iterable to a list.

  list("abc")  # Output: ['a', 'b', 'c']
  

• tuple(iterable): Converts an iterable to a tuple.

  tuple([1, 2, 3])  # Output: (1, 2, 3)
  

• dict(): Creates a dictionary.

  dict(a=1, b=2)  # Output: {'a': 1, 'b': 2}
  

• set(iterable): Converts an iterable to a set (removing duplicates).

  set([1, 2, 2, 3])  # Output: {1, 2, 3}
  

• bool(x): Converts x to a boolean (True or False).

  bool(1)  # Output: True
  bool(0)  # Output: False
  

3. Iterables and Iterator Functions

• len(s): Returns the length of an object (string, list, etc.).

  len("hello")  # Output: 5
  

• range(start, stop, step): Returns a sequence of numbers from start to stop (exclusive).

  list(range(1, 5))  # Output: [1, 2, 3, 4]
  

• map(function, iterable): Applies a function to each item in the iterable and returns a map object.

  list(map(str, [1, 2, 3]))  # Output: ['1', '2', '3']
  

• filter(function, iterable): Filters items from an iterable based on a condition in the function.

  list(filter(lambda x: x > 2, [1, 2, 3]))  # Output: [3]
  

• zip(*iterables): Combines elements from multiple iterables into tuples.

  list(zip([1, 2, 3], ['a', 'b', 'c']))  # Output: [(1, 'a'), (2, 'b'), (3, 'c')]
  

• enumerate(iterable): Returns an iterator that produces tuples of an index and an element from the iterable.

  list(enumerate(['a', 'b', 'c']))  # Output: [(0, 'a'), (1, 'b'), (2, 'c')]
  

4. Input/Output Functions

• print(*objects): Prints the specified objects to the console.

  print("Hello, world!")  # Output: Hello, world!
  

• input(prompt): Takes input from the user as a string.

  name = input("Enter your name: ")
  

• open(file, mode): Opens a file and returns a file object.

  file = open("example.txt", "r")
  

5. Object and Type-Related Functions

• type(x): Returns the type of an object.

  type(10)  # Output: <class 'int'>
  

• isinstance(obj, class): Checks if an object is an instance of a class.

  isinstance(10, int)  # Output: True
  

• id(x): Returns the unique identifier of an object.

  id(10)  # Output: unique memory address
  

• dir([object]): Returns a list of attributes and methods of an object.

  dir([])  # Output: List of list attributes and methods
  

• hasattr(object, name): Checks if an object has a specified attribute.

  hasattr(obj, 'attribute_name')
  

• setattr(object, name, value): Sets an attribute of an object to a specific value.

  setattr(obj, 'attribute_name', value)
  

• getattr(object, name): Returns the value of a specified attribute of an object.

  getattr(obj, 'attribute_name')
  

• delattr(object, name): Deletes an attribute from an object.

  delattr(obj, 'attribute_name')
  

6. Advanced Functions

• eval(expression): Evaluates a string expression as Python code.

  eval('2 + 2')  # Output: 4
  

• exec(object): Executes a string or object as Python code.

  exec('print("Hello, world!")')
  

• callable(object): Returns True if the object appears to be callable (e.g., functions or classes).

  callable(print)  # Output: True
  

7. Others

• help([object]): Provides help documentation for an object.

  help(print)
  

• sorted(iterable, key=None, reverse=False): Returns a sorted list of the specified iterable.

  sorted([3, 1, 2])  # Output: [1, 2, 3]
  

• reversed(sequence): Returns a reverse iterator of the given sequence.

  list(reversed([1, 2, 3]))  # Output: [3, 2, 1]
  

• any(iterable): Returns True if at least one element of the iterable is true.

  any([0, 1, 0])  # Output: True
  

• all(iterable): Returns True if all elements of the iterable are true.

  all([1, 2, 3])  # Output: True
  

Summary:

• Python provides a wide array of built-in functions that help in performing various common tasks.
• Functions such as print(), len(), sum(), map(), and filter() are useful in everyday programming.
• Type conversion functions like int(), str(), list(), and set() are useful for converting between types.
• Functions like eval(), exec(), help(), and dir() provide powerful tools for introspection and dynamic code execution.