Function Statement and Function Call

Python Tutorials - Herong's Tutorial Examples

∟Function Statement and Function Call

This chapter provides introductions and tutorial examples on user defined functions. Topics include defining and calling a function; assigning calling arguments to function parameters; returning object to the calling code; local, enclosing and global variables; using built-in functions; using lambda expression to create anonymous function.

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What Is Function

Built-In Functions

"def" Statement - Define Functions

"f(...)" - Function Call Operation

What Is Function Parameter

What Is Function Call Argument

Assign Function Call Arguments to Parameters

Special Function Parameters - "*" and "/"

"return" Statement Used in Functions

Variable Scope: LEGB (Local, Enclosing, Global, Built-in)

"global" Statement - Declare Global Variables Locally

"nonlocal" Statement - Declare Enclosing Variables Locally

"lambda" Expression - Simple Anonymous Function

Takeaways:

A function represents a block of sub-statements that can be called later to perform a specific function.
A built-in function is a function provided by the Python system.
"def f(parameter_list)" statements allow you to create user-defined function.
"f(argument_list)" represents a function call operation to execute a given function.
A parameter is a local variable declared in a function to receive an object reference from the calling code.
A starred parameter can receive multiple positional parameters as "tuple" object.
A double-starred parameter can receive multiple keyword parameters as "dict" object.
An argument is an object reference to be assigned to a function parameter in a function call operation.
"return object" statements allow you terminate the function and return the given object.
A local variable is a variable defined locally inside a function. It is considered to be in the local scope and accessible only in the defining function.
A global variable is a variable defined globally in the main code block. It is considered to be in the global scope and accessible everywhere.
An enclosing variable is a variable defined in enclosing functions. It is considered to be in the enclosing scope, and accessible in the defining function tree.
"global x" statements allow you to declare a global variable inside a function.
"nonlocal x" statements allow you to declare an enclosing variable in the nearest enclosing function.
"lambda" expression creates a "function" object which can be called to evaluate a parameterized sub-expression.