How to argue with functions
In this section we will look at how to write functions and call them. There are two types of arguments for functions
- Positional Arguments
- Keyword Arguments
Positional Arguments
For example for the given function
def addressbook(firstname, lastname, age, address=''):
print(f'Name: {firstname} {lastname} \nAge: {age} \naddress: {address}')
if we pass in addressbook('Jason', 'Bourne', 40, 'unknown')
then all the arguments are positional arguments. Because values are automatically assigned to variables at defined at that position.
Keyword Arguments, a better way to call functions
Python allows caller to call a function by passing parameters with parameter_name=value syntax. This is called keyword argument syntax
We can call the above function by keyword argument syntax.
addressbook(lastname='bourne',
firstname='jason',
address='unknown',
age=40)
Calling a function with keyword arguments is a better approach because it improves code readibility. With keyword argument syntax you can pass parameters in any order.
Forcing keyword arguments
You can also force callers of your function to use keyword arguments rather than using positional parameters. This is achieved by placing * in the function definition from where the keyword arguments should start. * can be at any position. In the below example it is at second position
Unknown number of arguments
Sometimes you need to pass unknown number of arguments to functions. They could be plain arguments or keyword arguments.
All non keyword argments become a tuple. In below example phonenumber is a tuple contains all the phone numbers. Remember the syntax the function declaration should have *phonenumber. Default naming convention is *args
All keyword arguments become a dictionary. In below example info is a dict.
Remember the syntax the function declaration should have **info. Default naming convention is **kwargs
