Python help() function

The Python help() function is used to get the documentation of specified modules, classes, functions, variables, etc. This method is generally used with the Python interpreter console to get details about Python objects.

Usage of Python help() Function

Python help() function syntax is:

help([object])

If no argument is given, the interactive help system starts on the interpreter console.

In the Python help console, we can specify module, class, function names to get their help documentation. Some examples include:

help> True
help> collections
help> builtins
help> modules
help> keywords
help> symbols
help> topics
help> LOOPING

If you want to get out of help console, type quit. We can also get the help documentation directly from the python console by passing a parameter to help() function.

>>> help('collections')
>>> help(print)
>>> help(globals)

Let’s see what is the output of the help() function for the globals() function.

>>> help('builtins.globals')

Help on built-in function globals in builtins:

builtins.globals = globals()
    Return the dictionary containing the current scope's global variables.
    
    NOTE: Updates to this dictionary *will* affect name lookups in the current global scope and vice-versa.

Defining help() for Custom Classes and Functions

We can define the help() function output for our custom classes and functions by defining a docstring (documentation string). The first comment string in the body of a method is usually used as its docstring, surrounded by three double quotes. Let’s say we have a python file python_help_examples.py with following code.

def add(x, y):
    """
    This function adds the given integer arguments
    :param x: integer
    :param y: integer
    :return: integer
    """
    return x + y


class Employee:
    """
    Employee class, mapped to "employee" table in Database
    """
    id = 0
    name = ''

    def __init__(self, i, n):
        """
        Employee object constructor
        :param i: integer, must be positive
        :param n: string
        """
        self.id = i
        self.name = n

Notice that we have defined docstring for function, class and its methods. You should follow some format for documentation, I have generated some part of them automatically using PyCharm IDE. Let’s see how to get this docstring as help documentation in python console. First of all, we will have to execute this script in the console to load our function and class definition. We can do this using exec() command.

>>> exec(open("python_help_examples.py").read())

We can verify that the functions and class definitions are present using globals() command.

>>> globals()
{'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <class '_frozen_importlib.BuiltinImporter'>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, '__warningregistry__': {'version': 0}, 'add': , 'Employee': <class '__main__.Employee'>}

Notice that ‘Employee’ and ‘add’ are present in the global scope dictionary. Now we can get the help documentation using help() function. Let’s look at some of the examples.

>>> help('python_help_examples')

>>> help('python_help_examples.add')

Help on function add in python_help_examples:

python_help_examples.add = add(x, y)
    This function adds the given integer arguments
    :param x: integer
    :param y: integer
    :return: integer
(END)

>>> help('python_help_examples.Employee')

>>> help('python_help_examples.Employee.__init__')


Help on function __init__ in python_help_examples.Employee:

python_help_examples.Employee.__init__ = __init__(self, i, n)
    Employee object constructor
    :param i: integer, must be positive
    :param n: string
(END)

Summary

The Python help() function is very helpful for getting details about modules, classes, and functions. It's always the best practice to define docstrings for custom classes and functions to explain their usage.