Parameters and Arguments

Parameters

• A parameter is the variable listed inside the parenthesis in the function definition
• If there is more than one value, then all are separated by comma

Arguments

• An argument is the value that is sent to the function when it is called
• Bounding of parameters to arguments is done 1:1 and so there should be same number and type of arguments as mentioned in the parameter list

Example

def my_add(a,b):
    z = a + b
    return z
x= int(input("Enter first number"))
y= int(input("Enter second number"))
c = my_add(x,y)
print("Result of addition =",c)

In this example, a, b are parameters and x,y are arguments. The value of arguments x, y are assigned to the parameters a, b.

Different types of Function arguments

The following are the types of formal arguments

• Required arguments
• Keyword arguments
• Default arguments
• Variable length arguments (Arbitrary arguments)
• Arbitrary keyword arguments

Required arguments

• Required arguments are the arguments passed to a function in correct positional order
• The number of arguments in the function call should match exactly with the function definition

def printdata(name, sub, mark):
    print("Name =", name)
    print("Subject =", sub)
    print("Mark = ",mark)
print("Students Details")
printdata("Raji","Python",95)
Students Details
('Name =', 'Raji')
('Subject =', 'Python')
('Mark = ', 95)

Keyword arguments

• Keyword arguments are send as key = value
• The order of the arguments does not matter in keyword arguments
• Rule: A non keyword argument after keyword arguments is not allowed.

Example

printdata(“def”, sub=”English”, 100) leads to error

def printdata(name, sub, mark):
    print("Name =", name)
    print("Subject =", sub)
    print("Mark = ",mark)
print("Students Details")
printdata(name="Raji", sub = "Python", mark=100)
printdata(sub = "physics", name = "ABC", mark = 98)
printdata(mark= 95, name="xyz", sub = "chemistry")
printdata("uvw","Maths",mark = 100)

Output

Students Details
('Name =', 'Raji')
('Subject =', 'Python')
('Mark = ', 100)
('Name =', 'ABC')
('Subject =', 'physics')
('Mark = ', 98)
('Name =', 'xyz')
('Subject =', 'chemistry')
('Mark = ', 95)
('Name =', 'uvw')
('Subject =', 'Maths')
('Mark = ', 100)

Default arguments

• If a value is not provided in the function call for a particular argument, then the default value specified in the function parameter is assumed for that argument
• Default arguments should be assigned from left to right i.e. without while calling a function default value will be assigned from left to right

def printdata(name="abc", mark=98):
    print("Name=", name)
    print("mark =",mark)
printdata("Raji") # passing only one argument
printdata("xyz",100) #passing both arguments

Output

('Name=', 'Raji')
('mark =', 98)
('Name=', 'xyz')
('mark =', 100)

Variable length arguments

• If the number of arguments passed to a function is unknown, then a * is added before the parameter name in the function definition
• In this way, the function will receive a tuple of arguments and can access the items accordingly

def printdata(*args):
    print("Subjects are", args)
    print("Subject  in args[0] ", args[0])
    print("Subject  in args[1] ", args[1])
    print("Subject  in args[2]",args[2])

printdata("python","chemistry", "physics")

Output

('Subjects are', ('python', 'chemistry', 'physics'))
('Subject  in args[0] ', 'python')
('Subject  in args[1] ', 'chemistry')
('Subject  in args[2]', 'physics')

Arbitrary keyword arguments

• If the number of keyword arguments to pass to the function is not known, then add two asterisk * before the parameter name in the function definition
• This way the function will receive the dictionary of arguments

def myfun(**Fullname):
    print("Full name is "+Fullname['fname']+Fullname['lname'])
myfun(fname="John", lname="Tomas")

Output

Full name is JohnTomas

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