Certainly, let’s break down functions, function parameters, and built-in functions in Python.

1. Functions

  • Concept: In essence, a function is a reusable block of code designed to perform a specific task. They promote code organization, reusability, and modularity.

  • Structure:

1def function_name(parameter1, parameter2, ...):  # Function definition (header)
2    """Docstring (optional): Briefly describe the function."""
3    # Code block to execute (body)
4    # ...
5    return some_value  # Optional: Returns a result
  • Example:
1def greet(name):
2    """This function greets the person passed in as a parameter."""
3    print(f"Hello, {name}!")
4
5greet("Alice")  # Function call
  • Key Points:
    • Functions are defined using the def keyword.
    • They can accept zero or more parameters (inputs).
    • The return statement (optional) sends a value back from the function.

2. Function Parameters (Arguments)

  • Purpose: Parameters act as placeholders for values you want to pass into a function when calling it. They make functions more flexible.

  • Types:

    • Positional Parameters: Must be passed in the exact order defined in the function definition.
    • Keyword Arguments: Passed with names, allowing you to specify which parameter each value corresponds to.
    • Default Parameters: Have predefined values, making them optional during the function call.

  • Example:

1def describe_pet(pet_name, animal_type="dog"):
2    """This function describes a pet."""
3    print(f"I have a {animal_type}.")
4    print(f"My {animal_type}'s name is {pet_name.title()}.")
5
6describe_pet("buddy")  # Uses the default 'dog'
7describe_pet("whiskers", "cat")  # Keyword argument

3. Built-in Functions

  • Definition: Python comes equipped with a set of pre-written, ready-to-use functions that provide common operations.

Basic Functions:

  • print(): Displays output on the console.
  • input(): Takes input from the user.
  • len(): Returns the length of a sequence (string, list, tuple, etc.).
  • type(): Returns the type of an object.
  • id(): Returns the unique identity of an object.
  • help(): Provides documentation and usage information about Python objects.

Type Conversion Functions:

  • int(): Converts a value to an integer.
  • float(): Converts a value to a floating-point number.
  • str(): Converts a value to a string.
  • bool(): Converts a value to a Boolean (True or False).
  • list(): Converts a sequence to a list.
  • tuple(): Converts a sequence to a tuple.
  • set(): Creates a set from a sequence.
  • dict(): Creates a dictionary from key-value pairs.

Mathematical Functions:

  • abs(): Returns the absolute value of a number.
  • round(): Rounds a number to a specified number of digits.
  • pow(): Raises a number to a given power.
  • max(): Returns the largest item in an iterable.
  • min(): Returns the smallest item in an iterable.
  • sum(): Returns the sum of all items in an iterable.
  • divmod(): Returns the quotient and remainder of a division.

Sequence Operations:

  • sorted(): Returns a new sorted list from the given iterable.
  • reversed(): Returns a reverse iterator of a sequence.
  • enumerate(): Returns an iterator of tuples (index, value) from a sequence.
  • zip(): Combines elements from multiple iterables into tuples.
  • all(): Returns True if all elements in an iterable are True.
  • any(): Returns True if any element in an iterable is True.

File Handling (requires open() function):

  • open(): Opens a file and returns a file object.
  • read(): Reads the content of a file.
  • write(): Writes data to a file.
  • close(): Closes an open file.

Other Important Built-in Functions:

  • range(): Generates a sequence of numbers.
  • isinstance(): Checks if an object is an instance of a specified class.
  • issubclass(): Checks if a class is a subclass of another class.
  • eval(): Executes a string as a Python expression.
  • exec(): Executes a string as Python code.
  • globals(): Returns a dictionary of the current global symbol table.
  • locals(): Returns a dictionary of the current local symbol table.

Notes

  • Functions encapsulate code for reusability and clarity.
  • Parameters provide inputs to functions, enhancing their flexibility.
  • Built-in functions offer convenient tools for common tasks, saving you from writing repetitive code.

Read: Python Console: input and output