The *args

Part of the Object Oriented Programming section of Coddy's Python journey — lesson 42 of 64.

The *args parameter allows a method to accept any number of positional arguments. The asterisk collects all extra positional arguments into a tuple.

Here is an example of a method using *args:

class Calculator:
    def add_numbers(self, *args):
        return sum(args)
    
    def show_numbers(self, *args):
        for i, num in enumerate(args):
            print(f"Number {i+1}: {num}")

Call the method with different numbers of arguments:

calc = Calculator()
result1 = calc.add_numbers(1, 2, 3)
result2 = calc.add_numbers(10, 20, 30, 40, 50)
print(result1)  # 6
print(result2)  # 150

The *args collects all arguments into a tuple:

calc.show_numbers(5, 10, 15, 20)

Output:

Number 1: 5
Number 2: 10
Number 3: 15
Number 4: 20

Combine regular parameters with *args:

class Logger:
    def log_message(self, level, *messages):
        print(f"[{level}]", end=" ")
        for message in messages:
            print(message, end=" ")
        print()  # New line

logger = Logger()
logger.log_message("INFO", "User", "logged", "in")
logger.log_message("ERROR", "Connection", "failed")

Use *args in constructor methods:

class Team:
    def __init__(self, team_name, *players):
        self.team_name = team_name
        self.players = list(players)
    
    def show_team(self):
        print(f"Team: {self.team_name}")
        for player in self.players:
            print(f"- {player}")

team = Team("Warriors", "Alice", "Bob", "Charlie", "Diana")
team.show_team()

Output:

6
150
Number 1: 5
Number 2: 10
Number 3: 15
Number 4: 20
[INFO] User logged in 
[ERROR] Connection failed 
Team: Warriors
- Alice
- Bob
- Charlie
- Diana

You can also unpack arguments when calling methods:

numbers = [1, 2, 3, 4, 5]
result = calc.add_numbers(*numbers)  # Unpacks the list
print(result)  # 15

Key Point: *args collects any number of positional arguments into a tuple. Use it when you don't know how many arguments will be passed to a method. The name args is conventional - you could use any name after the asterisk, but args is the standard.

Challenge

Easy

In this challenge, you'll implement a flexible number utility function.

Edit the number_utils.py file to implement the sum_all_numbers function that accepts any number of numeric arguments and returns their sum. The function should:

Return 0 if no arguments are provided
Print "Error: All arguments must be numbers" and return None if any non-numeric arguments are provided

The number_utils.py file contains detailed TODO comments to guide your implementation. Follow these comments carefully to ensure your solution meets all requirements.

Cheat sheet

The *args parameter allows a method to accept any number of positional arguments. The asterisk collects all extra positional arguments into a tuple.

Basic usage of *args:

class Calculator:
    def add_numbers(self, *args):
        return sum(args)

calc = Calculator()
result1 = calc.add_numbers(1, 2, 3)  # 6
result2 = calc.add_numbers(10, 20, 30, 40, 50)  # 150

Combine regular parameters with *args:

class Logger:
    def log_message(self, level, *messages):
        print(f"[{level}]", end=" ")
        for message in messages:
            print(message, end=" ")
        print()

logger = Logger()
logger.log_message("INFO", "User", "logged", "in")

Use *args in constructor methods:

class Team:
    def __init__(self, team_name, *players):
        self.team_name = team_name
        self.players = list(players)

team = Team("Warriors", "Alice", "Bob", "Charlie")

Unpack arguments when calling methods:

numbers = [1, 2, 3, 4, 5]
result = calc.add_numbers(*numbers)  # Unpacks the list

Key Point: *args collects any number of positional arguments into a tuple. The name args is conventional but you can use any name after the asterisk.

Try it yourself

from number_utils import sum_all_numbers

# Comprehensive test case handler
test_case = input()

if test_case == "basic_test":
    # Test basic functionality with positive integers
    print(sum_all_numbers(1, 2, 3))  # Should return 6
    print(sum_all_numbers())  # Should return 0
    print(sum_all_numbers(10, 20, 30, 40))  # Should return 100
    print(sum_all_numbers(1, 2, "three"))  # Should print error and return None

elif test_case == "float_test":
    # Test with floating point numbers
    print(sum_all_numbers(1.1, 2.2, 3.3))  # Should return 6.6
    print(sum_all_numbers(5.5, 5.0))  # Should return 10.5

elif test_case == "mixed_numbers_test":
    # Test with a mix of integers and floats
    print(sum_all_numbers(5, 5.5))  # Should return 10.5
    print(sum_all_numbers(10, 20.5, 30, 40))  # Should return 100.5

elif test_case == "zero_values_test":
    # Test with zero values
    print(sum_all_numbers(0, 0, 0))  # Should return 0
    print(sum_all_numbers(0))  # Should return 0
    print(sum_all_numbers())  # Should return 0

elif test_case == "negative_values_test":
    # Test with negative values
    print(sum_all_numbers(-1, -2, -3))  # Should return -6
    print(sum_all_numbers(-5, -5))  # Should return -10
    print(sum_all_numbers(-5, 5))  # Should return 0

elif test_case == "large_values_test":
    # Test with very large values
    print(sum_all_numbers(1000000000, 1000000000))  # Should return 2000000000
    print(sum_all_numbers(1000000000, 2000000000.5))  # Should return 3000000000.5

elif test_case == "single_value_test":
    # Test with a single value
    print(sum_all_numbers(5))  # Should return 5
    print(sum_all_numbers(-10))  # Should return -10
    print(sum_all_numbers(3.5))  # Should return 3.5

elif test_case == "error_handling_test":
    # Test with various non-numeric values
    print(sum_all_numbers("string"))  # Should print error and return None
    print(sum_all_numbers([1, 2, 3]))  # Should print error and return None
    print(sum_all_numbers({"key": "value"}))  # Should print error and return None
    print(sum_all_numbers(True))  # Should print error and return None
    print(sum_all_numbers(None))  # Should print error and return None

elif test_case == "mixed_valid_invalid_test":
    # Test with a mix of valid and invalid values
    print(sum_all_numbers(1, 2, "three"))  # Should print error and return None
    print(sum_all_numbers(1, [2, 3], 4))  # Should print error and return None
    print(sum_all_numbers(1.5, "two", 3))  # Should print error and return None

elif test_case == "empty_args_test":
    # Test with no arguments
    print(sum_all_numbers())  # Should return 0