[PriP 1.1] Revision Tour-1 – Practical 1.1

3. In each of the following parts there is an error in the Python code. Identify the error by name and describe the problem. (Each piece of code is prefixed with a brief description of the programmer’s intention.)

1. The following code attempts to compute the product of m and x added to b and assign that value to y.
   y = mx + b
2. The following code attempts to compute the first-order effects of some physical process. You may assume that equation is correct.
   cofactor = alpha * x * x
   1storder = 1.0 / cofactor
   2ndorder = 2.0 ** 1storder

Solution:

1. Error – NameError: It can also be stated as an operator issue. The error here is that the code is missing a multiplication sign or an arithmetic operator.
   Error Description: The NameError occurs because the variable mx is referenced before it has been defined. Python treats mx as a variable name, but it has not been assigned any value, leading to the NameError. The error is displayed in the console as:
   NameError: name 'mx' is not defined
   Also, the correct code though not asked for should be:
   y = m * x + b
2. Error – SyntaxError: It can also be stated as an identifier issue. The error lies in using numerical values (1storder and 2ndorder) as identifiers for variables. In Python, identifiers cannot start with a numerical digit.
   Error Description: The Python interpreter will raise a SyntaxError when encountering numerical identifiers like 1storder and 2ndorder because identifiers in Python cannot start with a numerical digit. This will prevent the code from executing successfully. The error will be displayed in the console as:
   SyntaxError: invalid syntax
   • Advanced Interpretation for Geeks: There’s always this identifier issue with the code, but there’s also this neglected part of code which could create potential division by zero errors or inaccuracies in computations. Though, it’s not mandatory to patch it, but it could prove as a bug in future interactions with the program.
   • The code attempts to compute the first-order effects of some physical process. The equation cofactor = alpha * x * x is given, and then 1storder is assigned as 1.0 / cofactor. Finally, 2ndorder is assigned as 2.0 ** 1storder.
   • The issue with this code is that it tries to compute the reciprocal of cofactor (which could potentially be zero), and then raises 2.0 to the power of that result. This might lead to a division by zero error if cofactor is equal to zero, resulting in a runtime error.
   • To fix this, one should first check if cofactor is not zero before attempting to compute its reciprocal.
     • Detailed Explanation:
     • If any of the factors α or x is equal to zero, the product will be zero regardless of the value of the other factor. This results in a cofactor of zero.
     • Even if α and x are both non-zero, if the value of x is extremely small (close to zero) or α is extremely large, the product α×x×x could approach zero, resulting in a cofactor very close to zero.

Finally, the corrected code though not asked for, is required for us to look upon and learn from.

cofactor = alpha * x * x

# Check if cofactor is not zero before computing reciprocal
if cofactor != 0:
    first_order = 1.0 / cofactor
    second_order = 2.0 ** first_order
else:
    print("Error: Division by zero")