Duplicated code

“Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.”

Antoine de Saint-Exupéry

Duplicated code occurs when similar or identical blocks of code appear multiple times within a codebase. This can increase maintenance efforts, as changes in one place might require corresponding changes elsewhere, leading to inconsistencies and higher changes or errors.

Symptoms

• The same logic appears in multiple places, sometimes with minor variations.
• Fixing a bug required modifying the same code in multiple places.
• Adding a new feature results in copy-pasting existing code rather than reusing it.

Example - Duplicate code in functions

def time_of_flight_ball(initial_velocity, launch_angle):
    g = 9.81  # Earth's gravity (m/s²)
    return (2 * initial_velocity * np.sin(launch_angle)) / g

def time_of_flight_rocket(initial_velocity, launch_angle):
    g = 9.81
    return (2 * initial_velocity * np.sin(launch_angle)) / g

def time_of_flight_satellite(initial_velocity, launch_angle):
    g = 9.81
    return (2 * initial_velocity * np.sin(launch_angle)) / g

Solution

• Refactor the code to accept parameters as arguments, instead of hard-coding them.
• Extract common functionality into functions or methods.
• Refactor duplicated code into higher-level abstractions.
• Make use of utility functions to centralize common code and avoid duplication.

def time_of_flight(initial_velocity, launch_angle, gravity=9.81):
    """Compute time of flight for any projectile."""
    return (2 * initial_velocity * np.sin(launch_angle)) / gravity

# Usage
tof_ball = time_of_flight(30, np.pi/4)       # Time of flight for a ball
tof_rocket = time_of_flight(100, np.pi/3)    # Time of flight for a rocket
tof_mars_probe = time_of_flight(300, np.pi/6, gravity=3.71)  # Gravity adjusted for Mars

Key takeaways

• Extracting common functionality into functions or methods can help reduce duplication and improve code reuse.