Function Arguments in Python: Positional & Keyword Mechanics0%

Function Arguments in Python: Positional & Keyword Mechanics

Beginner12 min read•Updated: 2026-09-30

Function Arguments in Python: Positional & Keyword Mechanics

When invoking functions, passing data into them reliably is essential. To master function calls, you must first understand the distinction between two related terms:

Parameter: The placeholder variable defined in the function's header (def calculate_emi(principal, tenure):).
Argument: The concrete value passed into the function when invoking it (calculate_emi(500000, 5)).

Python provides two distinct ways to bind arguments to parameters: Positional Arguments (matched by sequential order) and Keyword Arguments (matched by parameter name).

Real-World Analogy: Physical Assembly Line vs. Courier Parcel Labels

Visual Architecture Blueprint

+-------------------------------------------------------------------------------+
|                    ARGUMENT BINDING REAL-WORLD ANALOGIES                      |
+-------------------------------------------------------------------------------+

  1. THE FACTORY CONVEYOR BELT (Positional Arguments):
     - An assembly worker receives three slots: [Engine, Wheels, Chassis].
     - The parts arrive on a physical conveyor belt in strict sequence:
       Part 1 ALWAYS goes to Engine, Part 2 to Wheels, Part 3 to Chassis.
     - If the delivery order gets swapped, the machine assembles a backwards car!
     - Position and order dictate meaning.

  2. SPEED POST LABELED PARCELS (Keyword Arguments):
     - A courier delivery truck carries three labeled boxes:
       `recipient="Vikram"`, `pincode=110001`, `fragile=True`
     - The postal delivery driver can pull boxes out in ANY arbitrary order:
       the box marked `pincode=110001` will ALWAYS go to the pincode slot,
       because the explicit label guarantees unambiguous routing.
+-------------------------------------------------------------------------------+

Visual Architecture: Positional vs. Keyword Binding

1================================================================================
                  ARGUMENT BINDING RESOLUTION
3================================================================================
4 
Function Definition:
def issue_ticket(passenger_name, source, destination, coach):
                        ^           ^          ^        ^
                        |           |          |        |
CASE A: Positional Call (Order Dictates Mapping)        |
issue_ticket(  "Aarav",   "NDLS",    "BSB",    "B3"  )
                 |           |          |        |
                 v           v          v        v
          passenger_name   source  destination coach
14 
CASE B: Keyword Call (Name Dictates Mapping - Order Irrelevant)
issue_ticket(destination="BSB", coach="B3", passenger_name="Aarav", source="NDLS")
                 |                |                 |                   |
                 +-- destination  +-- coach         +-- passenger_name  +-- source
19================================================================================

1. Positional Arguments (Order-Dependent)

Positional arguments are the default in most programming languages. Arguments are mapped one-to-one with parameters based strictly on their physical position from left to right:

1# ==========================================================
2# Example 1: Positional Argument Mapping
3# ==========================================================
4 
5def reserve_train_berth(passenger_name: str, train_no: int, berth_type: str):
6    print(f"Confirmed: {passenger_name} -> Train #{train_no} | Berth: {berth_type}")
7 
8# Valid positional call:
9reserve_train_berth("Rohan Verma", 12424, "Side Lower")
10 
11# DANGEROUS BUG: Swapping positions corrupts business logic!
12reserve_train_berth(12424, "Side Lower", "Rohan Verma")

Output:

1Confirmed: Rohan Verma -> Train #12424 | Berth: Side Lower
2Confirmed: 12424 -> Train #Side Lower | Berth: Rohan Verma

Notice how swapping the arguments in the second call corrupted the output without raising a syntax error!

2. Keyword Arguments (Named Parameter Binding)

Keyword arguments pass values in the format parameter_name = value. Because each value is explicitly labeled, the order in which they appear in the function call does not matter:

1# ==========================================================
2# Example 2: Keyword Arguments (Order Independence)
3# ==========================================================
4 
5def calculate_home_loan_emi(principal: float, annual_rate: float, tenure_years: int):
6    monthly_rate = (annual_rate / 12) / 100
7    months = tenure_years * 12
8    emi = (principal * monthly_rate * ((1 + monthly_rate) ** months)) / (((1 + monthly_rate) ** months) - 1)
9    return emi
10 
11# Called with explicit keyword labels in arbitrary order:
12emi_1 = calculate_home_loan_emi(principal=5000000.0, annual_rate=8.5, tenure_years=20)
13emi_2 = calculate_home_loan_emi(tenure_years=20, principal=5000000.0, annual_rate=8.5)
14 
15print(f"EMI 1: Rs {emi_1:,.2f}")
16print(f"EMI 2: Rs {emi_2:,.2f} (Identical result despite scrambled order)")

Output:

1EMI 1: Rs 43,391.16
2EMI 2: Rs 43,391.16 (Identical result despite scrambled order)

3. Mixing Positional and Keyword Arguments: The Cardinal Rule

Python allows mixing positional and keyword arguments in the same function call. However, you must adhere strictly to The Cardinal Rule:

[!IMPORTANT] THE CARDINAL RULE: Positional arguments MUST ALWAYS precede keyword arguments! As soon as you provide a single keyword argument, all subsequent arguments in that call must also be keyword arguments.

1def configure_user_profile(user_id, username, email, is_admin):
2    print(f"ID: {user_id}, Name: {username}, Email: {email}, Admin: {is_admin}")
3 
4# VALID: Positional first, followed by keywords:
5configure_user_profile(101, "aditya_s", email="aditya@msk.in", is_admin=True)
6 
7# INVALID: Positional argument AFTER a keyword argument!
8# configure_user_profile(user_id=101, "aditya_s", email="aditya@msk.in", False)
9# SYNTAX ERROR: positional argument follows keyword argument

Preventing Duplicate Binding:

You cannot assign a value to the same parameter more than once:

1# INVALID: user_id received 101 positionally, and 999 via keyword!
2# configure_user_profile(101, "aditya_s", user_id=999, email="a@b.com", is_admin=False)
3# TYPE ERROR: configure_user_profile() got multiple values for argument 'user_id'

4. Enforcing Keyword-Only Arguments with `*`

Python allows function authors to enforce that certain critical arguments must always be passed as keywords. This is done by placing an asterisk * in the parameter list:

1# ==========================================================
2# Example 3: Keyword-Only Security Constraints
3# ==========================================================
4 
5# Parameters after '*' MUST be passed by keyword!
6def transfer_bank_funds(sender_acc: str, receiver_acc: str, amount_inr: float, *, require_otp: bool, is_neft: bool):
7    print(f"Transferring Rs {amount_inr:,.2f} from {sender_acc} -> {receiver_acc}")
8    print(f"  Security Flags: OTP Required={require_otp}, Mode={'NEFT' if is_neft else 'RTGS'}")
9 
10# VALID: Parameters after '*' are explicitly named
11transfer_bank_funds("SBI-1001", "HDFC-2002", 75000.0, require_otp=True, is_neft=True)
12 
13# INVALID: Calling with positional arguments after '*'
14# transfer_bank_funds("SBI-1001", "HDFC-2002", 75000.0, True, True)
15# TYPE ERROR: takes 3 positional arguments but 5 were given

Keyword-only parameters prevent accidental bugs when functions accept boolean flags.

5. Do's and Don'ts Best Practices

Best Practice (DO)	Dangerous Anti-Pattern (DON'T)
DO use positional arguments for natural primary inputs (e.g. `math.sin(x)`).	DON'T place positional arguments after keyword arguments (`SyntaxError`).
DO use keyword arguments for configuration options, optional flags, and boolean toggles.	DON'T supply multiple values for the same parameter both positionally and via keyword (`TypeError`).
DO use the `*` delimiter to enforce keyword-only arguments for safety-critical settings.	DON'T rely on positional arguments when a function accepts 5+ parameters; use keyword arguments for readability.

Quick Revision Summary

Positional arguments are bound to parameters strictly by order (from left to right).
Keyword arguments are explicitly labeled with name=value and can be supplied in any order.
In mixed calls, positional arguments must always come first; once a keyword argument is used, all remaining arguments must also be keywords.
Attempting to pass a positional argument after a keyword argument causes an immediate SyntaxError.
Placing an asterisk * in a parameter list marks all subsequent parameters as keyword-only.

⚠️ Common Beginner Mistakes & Gotchas

1. Forgetting the `return` Statement

If a function computes a value but doesn't return it, Python returns None by default:

1def add(a, b):
2    result = a + b
3    # Missing: return result
4 
5total = add(5, 10)
6print(total)  # None (not 15!)

2. Modifying Global Variables Without the `global` Keyword

Reading a global variable is permitted, but assigning to it creates a local variable unless explicitly declared:

1counter = 0
2 
3def increment():
4    global counter  # Required to modify global scope
5    counter += 1
6 
7increment()
8print(counter)  # 1

Interactive Quiz• Knowledge Check

Practice Quiz

1. What will happen if you run the following code?

1def greet(name, msg):
2    print(f"{msg}, {name}!")
3 
4greet(name="Karan", "Good Morning")

A. Output: Good Morning, Karan! B. SyntaxError: positional argument follows keyword argument C. TypeError: greet() takes 2 arguments but got 1 D. Output: None, Karan!

Answer: B

2. What is the output of the following function call?

1def describe_pet(animal_type, pet_name):
2    print(f"I have a {animal_type} named {pet_name}.")
3 
4describe_pet(pet_name="Sheru", animal_type="Dog")

A. I have a Sheru named Dog. B. I have a Dog named Sheru. C. TypeError: unexpected keyword order D. I have a animal_type named pet_name.

Answer: B

3. What error is raised by the following call?

1def display_info(user_id, role):
2    pass
3 
4display_info(101, "Admin", user_id=202)

A. SyntaxError: invalid syntax B. TypeError: got multiple values for argument 'user_id' C. ValueError: duplicate key D. NameError: user_id redefined

Answer: B

4. How can you define a function such that a parameter `debug_mode` can ONLY be passed as a keyword argument?

A. def log(msg, @debug_mode): B. def log(msg, *, debug_mode): C. def log(msg, kw_only(debug_mode)): D. def log(msg, kwargs: debug_mode):

Answer: B

5. What is the key difference between a parameter and an argument?

A. Parameters are used in loops; arguments are used in conditionals B. Parameters are variables defined in the function signature; arguments are the real values passed in during invocation C. Parameters must be strings; arguments must be numbers D. There is no difference; they are exact technical synonyms

Answer: B

Practice Challenge: Swiggy / Zomato Food Delivery Dispatch Engine

Build an automated order dispatch and delivery fee calculator for an Indian food delivery platform (Swiggy / Zomato).

Create a modular dispatch function: dispatch_food_order(customer_name, restaurant_name, distance_km, *, is_prime_member=False, applied_coupon="NONE", tip_inr=0.0)

Requirements:

1
customer_name, restaurant_name, and distance_km are positional arguments.
2
is_prime_member, applied_coupon, and tip_inr must be keyword-only arguments enforced by *.
3
Delivery Fee Calculation:

Base delivery fee: Rs 30 for the first 3 km.
For distance beyond 3 km: Rs 12 per additional km.
If is_prime_member == True: 100% discount on delivery fee (Free Delivery).

1
Discount Coupon:

"SWIGGYIT": Rs 50 off the final bill.
"ZOMATO50": 20% off the final bill (up to a max of Rs 100).

1
Print a formatted order dispatch slip and invoice breakdown.

Complete Solution

1# ==========================================================
2# Challenge: Food Delivery Dispatch Engine
3# ==========================================================
4 
5def dispatch_food_order(
  customer_name: str,
  restaurant_name: str,
  distance_km: float,
  cart_total_inr: float,
  *,
  is_prime_member: bool = False,
  applied_coupon: str = "NONE",
  tip_inr: float = 0.0
14) -> dict:
  """Dispatches food delivery order using positional and keyword-only arguments."""
  
  # 1. Delivery Fee Calculation
  if is_prime_member:
      delivery_fee = 0.0
  else:
      if distance_km <= 3.0:
          delivery_fee = 30.0
      else:
          delivery_fee = 30.0 + (distance_km - 3.0) * 12.0
          
  # 2. Coupon Discount Calculation
  discount = 0.0
  if applied_coupon == "SWIGGYIT":
      discount = 50.0
  elif applied_coupon == "ZOMATO50":
      discount = min(cart_total_inr * 0.20, 100.0)
      
  final_payable = (cart_total_inr - discount) + delivery_fee + tip_inr
  
  # Render Dispatch Slip
  print("+" + "=" * 54 + "+")
  print(f"| {'SWIGGY / ZOMATO ORDER DISPATCH SLIP':^52} |")
  print("+" + "=" * 54 + "+")
  print(f"  Customer:   {customer_name:<20} Prime: {'YES' if is_prime_member else 'NO'}")
  print(f"  Restaurant: {restaurant_name}")
  print(f"  Distance:   {distance_km:.1f} km")
  print("-" * 54)
  print(f"  Food Cart Total:     Rs {cart_total_inr:>8.2f}")
  print(f"  Coupon ({applied_coupon}):      -Rs {discount:>8.2f}")
  print(f"  Delivery Logistics:  Rs {delivery_fee:>8.2f}")
  print(f"  Rider Courtesy Tip:  Rs {tip_inr:>8.2f}")
  print("-" * 54)
  print(f"  FINAL AMOUNT TO PAY: Rs {final_payable:>8.2f}")
  print("+" + "=" * 54 + "+\n")
  
  return {
      "customer": customer_name,
      "final_payable": final_payable,
      "delivery_fee": delivery_fee
  }
56 
57# Test Invocations:
58 
59# Order 1: Standard customer, distance 6.5 km, tip given
60dispatch_food_order(
  "Arjun Kapoor", "Haldiram's Chandni Chowk", 6.5, 480.0,
  is_prime_member=False, applied_coupon="SWIGGYIT", tip_inr=30.0
63)
64 
65# Order 2: Prime Super Member, free delivery, Zomato discount
66dispatch_food_order(
  "Priya Nair", "Saravana Bhavan Connaught", 4.2, 650.0,
  is_prime_member=True, applied_coupon="ZOMATO50", tip_inr=50.0
69)

🚀 What's Next?

In the next lesson, we will continue your Python learning journey with *Arguments: Default, args, kwargs (14: Functions).

👉 *[Continue to Next Lesson: Arguments: Default, args, kwargs →](/tutorials/python-for-beginners/arguments-default-args-kwargs)

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Arguments: Default, *args, **kwargs

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

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Test your understanding of this lesson with 5 questions. Each question has one correct answer.

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Arguments: Default, *args, **kwargs

Function Arguments in Python: Positional & Keyword Mechanics

Beginner12 min read•Updated: 2026-09-30

Study Materials Cheatsheet

Function Arguments in Python: Positional & Keyword Mechanics

When invoking functions, passing data into them reliably is essential. To master function calls, you must first understand the distinction between two related terms:

Parameter: The placeholder variable defined in the function's header (def calculate_emi(principal, tenure):).
Argument: The concrete value passed into the function when invoking it (calculate_emi(500000, 5)).

Python provides two distinct ways to bind arguments to parameters: Positional Arguments (matched by sequential order) and Keyword Arguments (matched by parameter name).

Real-World Analogy: Physical Assembly Line vs. Courier Parcel Labels

Visual Architecture Blueprint

+-------------------------------------------------------------------------------+
|                    ARGUMENT BINDING REAL-WORLD ANALOGIES                      |
+-------------------------------------------------------------------------------+

  1. THE FACTORY CONVEYOR BELT (Positional Arguments):
     - An assembly worker receives three slots: [Engine, Wheels, Chassis].
     - The parts arrive on a physical conveyor belt in strict sequence:
       Part 1 ALWAYS goes to Engine, Part 2 to Wheels, Part 3 to Chassis.
     - If the delivery order gets swapped, the machine assembles a backwards car!
     - Position and order dictate meaning.

  2. SPEED POST LABELED PARCELS (Keyword Arguments):
     - A courier delivery truck carries three labeled boxes:
       `recipient="Vikram"`, `pincode=110001`, `fragile=True`
     - The postal delivery driver can pull boxes out in ANY arbitrary order:
       the box marked `pincode=110001` will ALWAYS go to the pincode slot,
       because the explicit label guarantees unambiguous routing.
+-------------------------------------------------------------------------------+

Visual Architecture: Positional vs. Keyword Binding

1================================================================================
                  ARGUMENT BINDING RESOLUTION
3================================================================================
4 
Function Definition:
def issue_ticket(passenger_name, source, destination, coach):
                        ^           ^          ^        ^
                        |           |          |        |
CASE A: Positional Call (Order Dictates Mapping)        |
issue_ticket(  "Aarav",   "NDLS",    "BSB",    "B3"  )
                 |           |          |        |
                 v           v          v        v
          passenger_name   source  destination coach
14 
CASE B: Keyword Call (Name Dictates Mapping - Order Irrelevant)
issue_ticket(destination="BSB", coach="B3", passenger_name="Aarav", source="NDLS")
                 |                |                 |                   |
                 +-- destination  +-- coach         +-- passenger_name  +-- source
19================================================================================

1. Positional Arguments (Order-Dependent)

Positional arguments are the default in most programming languages. Arguments are mapped one-to-one with parameters based strictly on their physical position from left to right:

1# ==========================================================
2# Example 1: Positional Argument Mapping
3# ==========================================================
4 
5def reserve_train_berth(passenger_name: str, train_no: int, berth_type: str):
6    print(f"Confirmed: {passenger_name} -> Train #{train_no} | Berth: {berth_type}")
7 
8# Valid positional call:
9reserve_train_berth("Rohan Verma", 12424, "Side Lower")
10 
11# DANGEROUS BUG: Swapping positions corrupts business logic!
12reserve_train_berth(12424, "Side Lower", "Rohan Verma")

Output:

1Confirmed: Rohan Verma -> Train #12424 | Berth: Side Lower
2Confirmed: 12424 -> Train #Side Lower | Berth: Rohan Verma

Notice how swapping the arguments in the second call corrupted the output without raising a syntax error!

2. Keyword Arguments (Named Parameter Binding)

Keyword arguments pass values in the format parameter_name = value. Because each value is explicitly labeled, the order in which they appear in the function call does not matter:

1# ==========================================================
2# Example 2: Keyword Arguments (Order Independence)
3# ==========================================================
4 
5def calculate_home_loan_emi(principal: float, annual_rate: float, tenure_years: int):
6    monthly_rate = (annual_rate / 12) / 100
7    months = tenure_years * 12
8    emi = (principal * monthly_rate * ((1 + monthly_rate) ** months)) / (((1 + monthly_rate) ** months) - 1)
9    return emi
10 
11# Called with explicit keyword labels in arbitrary order:
12emi_1 = calculate_home_loan_emi(principal=5000000.0, annual_rate=8.5, tenure_years=20)
13emi_2 = calculate_home_loan_emi(tenure_years=20, principal=5000000.0, annual_rate=8.5)
14 
15print(f"EMI 1: Rs {emi_1:,.2f}")
16print(f"EMI 2: Rs {emi_2:,.2f} (Identical result despite scrambled order)")

Output:

1EMI 1: Rs 43,391.16
2EMI 2: Rs 43,391.16 (Identical result despite scrambled order)

3. Mixing Positional and Keyword Arguments: The Cardinal Rule

Python allows mixing positional and keyword arguments in the same function call. However, you must adhere strictly to The Cardinal Rule:

1def configure_user_profile(user_id, username, email, is_admin):
2    print(f"ID: {user_id}, Name: {username}, Email: {email}, Admin: {is_admin}")
3 
4# VALID: Positional first, followed by keywords:
5configure_user_profile(101, "aditya_s", email="aditya@msk.in", is_admin=True)
6 
7# INVALID: Positional argument AFTER a keyword argument!
8# configure_user_profile(user_id=101, "aditya_s", email="aditya@msk.in", False)
9# SYNTAX ERROR: positional argument follows keyword argument

Preventing Duplicate Binding:

You cannot assign a value to the same parameter more than once:

1# INVALID: user_id received 101 positionally, and 999 via keyword!
2# configure_user_profile(101, "aditya_s", user_id=999, email="a@b.com", is_admin=False)
3# TYPE ERROR: configure_user_profile() got multiple values for argument 'user_id'

4. Enforcing Keyword-Only Arguments with `*`

Python allows function authors to enforce that certain critical arguments must always be passed as keywords. This is done by placing an asterisk * in the parameter list:

1# ==========================================================
2# Example 3: Keyword-Only Security Constraints
3# ==========================================================
4 
5# Parameters after '*' MUST be passed by keyword!
6def transfer_bank_funds(sender_acc: str, receiver_acc: str, amount_inr: float, *, require_otp: bool, is_neft: bool):
7    print(f"Transferring Rs {amount_inr:,.2f} from {sender_acc} -> {receiver_acc}")
8    print(f"  Security Flags: OTP Required={require_otp}, Mode={'NEFT' if is_neft else 'RTGS'}")
9 
10# VALID: Parameters after '*' are explicitly named
11transfer_bank_funds("SBI-1001", "HDFC-2002", 75000.0, require_otp=True, is_neft=True)
12 
13# INVALID: Calling with positional arguments after '*'
14# transfer_bank_funds("SBI-1001", "HDFC-2002", 75000.0, True, True)
15# TYPE ERROR: takes 3 positional arguments but 5 were given

Keyword-only parameters prevent accidental bugs when functions accept boolean flags.

5. Do's and Don'ts Best Practices

Best Practice (DO)	Dangerous Anti-Pattern (DON'T)
DO use positional arguments for natural primary inputs (e.g. `math.sin(x)`).	DON'T place positional arguments after keyword arguments (`SyntaxError`).
DO use keyword arguments for configuration options, optional flags, and boolean toggles.	DON'T supply multiple values for the same parameter both positionally and via keyword (`TypeError`).
DO use the `*` delimiter to enforce keyword-only arguments for safety-critical settings.	DON'T rely on positional arguments when a function accepts 5+ parameters; use keyword arguments for readability.

Quick Revision Summary

Positional arguments are bound to parameters strictly by order (from left to right).
Keyword arguments are explicitly labeled with name=value and can be supplied in any order.
In mixed calls, positional arguments must always come first; once a keyword argument is used, all remaining arguments must also be keywords.
Attempting to pass a positional argument after a keyword argument causes an immediate SyntaxError.
Placing an asterisk * in a parameter list marks all subsequent parameters as keyword-only.

⚠️ Common Beginner Mistakes & Gotchas

1. Forgetting the `return` Statement

If a function computes a value but doesn't return it, Python returns None by default:

1def add(a, b):
2    result = a + b
3    # Missing: return result
4 
5total = add(5, 10)
6print(total)  # None (not 15!)

2. Modifying Global Variables Without the `global` Keyword

Reading a global variable is permitted, but assigning to it creates a local variable unless explicitly declared:

1counter = 0
2 
3def increment():
4    global counter  # Required to modify global scope
5    counter += 1
6 
7increment()
8print(counter)  # 1

Interactive Quiz• Knowledge Check

Practice Quiz

1. What will happen if you run the following code?

1def greet(name, msg):
2    print(f"{msg}, {name}!")
3 
4greet(name="Karan", "Good Morning")

A. Output: Good Morning, Karan! B. SyntaxError: positional argument follows keyword argument C. TypeError: greet() takes 2 arguments but got 1 D. Output: None, Karan!

Answer: B

2. What is the output of the following function call?

1def describe_pet(animal_type, pet_name):
2    print(f"I have a {animal_type} named {pet_name}.")
3 
4describe_pet(pet_name="Sheru", animal_type="Dog")

A. I have a Sheru named Dog. B. I have a Dog named Sheru. C. TypeError: unexpected keyword order D. I have a animal_type named pet_name.

Answer: B

3. What error is raised by the following call?

1def display_info(user_id, role):
2    pass
3 
4display_info(101, "Admin", user_id=202)

A. SyntaxError: invalid syntax B. TypeError: got multiple values for argument 'user_id' C. ValueError: duplicate key D. NameError: user_id redefined

Answer: B

4. How can you define a function such that a parameter `debug_mode` can ONLY be passed as a keyword argument?

A. def log(msg, @debug_mode): B. def log(msg, *, debug_mode): C. def log(msg, kw_only(debug_mode)): D. def log(msg, kwargs: debug_mode):

Answer: B

5. What is the key difference between a parameter and an argument?

Answer: B

Practice Challenge: Swiggy / Zomato Food Delivery Dispatch Engine

Build an automated order dispatch and delivery fee calculator for an Indian food delivery platform (Swiggy / Zomato).

Create a modular dispatch function: dispatch_food_order(customer_name, restaurant_name, distance_km, *, is_prime_member=False, applied_coupon="NONE", tip_inr=0.0)

Requirements:

1
customer_name, restaurant_name, and distance_km are positional arguments.
2
is_prime_member, applied_coupon, and tip_inr must be keyword-only arguments enforced by *.
3
Delivery Fee Calculation:

Base delivery fee: Rs 30 for the first 3 km.
For distance beyond 3 km: Rs 12 per additional km.
If is_prime_member == True: 100% discount on delivery fee (Free Delivery).

1
Discount Coupon:

"SWIGGYIT": Rs 50 off the final bill.
"ZOMATO50": 20% off the final bill (up to a max of Rs 100).

1
Print a formatted order dispatch slip and invoice breakdown.

Complete Solution

1# ==========================================================
2# Challenge: Food Delivery Dispatch Engine
3# ==========================================================
4 
5def dispatch_food_order(
  customer_name: str,
  restaurant_name: str,
  distance_km: float,
  cart_total_inr: float,
  *,
  is_prime_member: bool = False,
  applied_coupon: str = "NONE",
  tip_inr: float = 0.0
14) -> dict:
  """Dispatches food delivery order using positional and keyword-only arguments."""
  
  # 1. Delivery Fee Calculation
  if is_prime_member:
      delivery_fee = 0.0
  else:
      if distance_km <= 3.0:
          delivery_fee = 30.0
      else:
          delivery_fee = 30.0 + (distance_km - 3.0) * 12.0
          
  # 2. Coupon Discount Calculation
  discount = 0.0
  if applied_coupon == "SWIGGYIT":
      discount = 50.0
  elif applied_coupon == "ZOMATO50":
      discount = min(cart_total_inr * 0.20, 100.0)
      
  final_payable = (cart_total_inr - discount) + delivery_fee + tip_inr
  
  # Render Dispatch Slip
  print("+" + "=" * 54 + "+")
  print(f"| {'SWIGGY / ZOMATO ORDER DISPATCH SLIP':^52} |")
  print("+" + "=" * 54 + "+")
  print(f"  Customer:   {customer_name:<20} Prime: {'YES' if is_prime_member else 'NO'}")
  print(f"  Restaurant: {restaurant_name}")
  print(f"  Distance:   {distance_km:.1f} km")
  print("-" * 54)
  print(f"  Food Cart Total:     Rs {cart_total_inr:>8.2f}")
  print(f"  Coupon ({applied_coupon}):      -Rs {discount:>8.2f}")
  print(f"  Delivery Logistics:  Rs {delivery_fee:>8.2f}")
  print(f"  Rider Courtesy Tip:  Rs {tip_inr:>8.2f}")
  print("-" * 54)
  print(f"  FINAL AMOUNT TO PAY: Rs {final_payable:>8.2f}")
  print("+" + "=" * 54 + "+\n")
  
  return {
      "customer": customer_name,
      "final_payable": final_payable,
      "delivery_fee": delivery_fee
  }
56 
57# Test Invocations:
58 
59# Order 1: Standard customer, distance 6.5 km, tip given
60dispatch_food_order(
  "Arjun Kapoor", "Haldiram's Chandni Chowk", 6.5, 480.0,
  is_prime_member=False, applied_coupon="SWIGGYIT", tip_inr=30.0
63)
64 
65# Order 2: Prime Super Member, free delivery, Zomato discount
66dispatch_food_order(
  "Priya Nair", "Saravana Bhavan Connaught", 4.2, 650.0,
  is_prime_member=True, applied_coupon="ZOMATO50", tip_inr=50.0
69)

🚀 What's Next?

In the next lesson, we will continue your Python learning journey with *Arguments: Default, args, kwargs (14: Functions).

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Arguments: Default, *args, **kwargs

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Defining & Calling Functions	Arguments: Default, args, *kwargs

Practice Quiz

Test your understanding of this lesson with 5 questions. Each question has one correct answer.

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Function Arguments in Python: Positional & Keyword Mechanics

Real-World Analogy: Physical Assembly Line vs. Courier Parcel Labels

Visual Architecture: Positional vs. Keyword Binding

1. Positional Arguments (Order-Dependent)

2. Keyword Arguments (Named Parameter Binding)

3. Mixing Positional and Keyword Arguments: The Cardinal Rule

Preventing Duplicate Binding:

4. Enforcing Keyword-Only Arguments with *

5. Do's and Don'ts Best Practices

Quick Revision Summary

⚠️ Common Beginner Mistakes & Gotchas

1. Forgetting the return Statement

2. Modifying Global Variables Without the global Keyword

Practice Quiz

1. What will happen if you run the following code?

2. What is the output of the following function call?

3. What error is raised by the following call?

4. How can you define a function such that a parameter debug_mode can ONLY be passed as a keyword argument?

5. What is the key difference between a parameter and an argument?

Practice Challenge: Swiggy / Zomato Food Delivery Dispatch Engine

Requirements:

Complete Solution

🚀 What's Next?

Arguments: Default, *args, **kwargs

Related Lessons

Practice Quiz

Loading Page Content...

Function Arguments in Python: Positional & Keyword Mechanics

Real-World Analogy: Physical Assembly Line vs. Courier Parcel Labels

Visual Architecture: Positional vs. Keyword Binding

1. Positional Arguments (Order-Dependent)

2. Keyword Arguments (Named Parameter Binding)

3. Mixing Positional and Keyword Arguments: The Cardinal Rule

Preventing Duplicate Binding:

4. Enforcing Keyword-Only Arguments with *

5. Do's and Don'ts Best Practices

Quick Revision Summary

⚠️ Common Beginner Mistakes & Gotchas

1. Forgetting the return Statement

2. Modifying Global Variables Without the global Keyword

Practice Quiz

1. What will happen if you run the following code?

2. What is the output of the following function call?

3. What error is raised by the following call?

4. How can you define a function such that a parameter debug_mode can ONLY be passed as a keyword argument?

5. What is the key difference between a parameter and an argument?

Practice Challenge: Swiggy / Zomato Food Delivery Dispatch Engine

Requirements:

Complete Solution

🚀 What's Next?

Arguments: Default, *args, **kwargs

Related Lessons

Practice Quiz

4. Enforcing Keyword-Only Arguments with `*`

1. Forgetting the `return` Statement

2. Modifying Global Variables Without the `global` Keyword

4. How can you define a function such that a parameter `debug_mode` can ONLY be passed as a keyword argument?

4. Enforcing Keyword-Only Arguments with `*`

1. Forgetting the `return` Statement

2. Modifying Global Variables Without the `global` Keyword

4. How can you define a function such that a parameter `debug_mode` can ONLY be passed as a keyword argument?