Given this code

for i in [2, 4, 6, 8]:

Why is i discouraged as a loop variable name?

Question

Given this code

for i in [2, 4, 6, 8]:

Why is i discouraged as a loop variable name?

BlackTom AI · Accepted Answer

The question presents a code snippet and asks why i is discouraged as a loop variable name. However, the provided data lacks the answer choices, so we cannot evaluate which option corresponds to the expected rationale. Instead, we can reason about why using i as a loop variable name is generally discouraged in Python and similar languages, and what a better practice would be.

First, consider the historical and conventional use of i: in many tutorials and math texts, i is used as a generic loop or index variable. That historical baggage can mislead readers into thinking i always represents an index or position in a sequence. In Python and other modern languages, loop variables are often used for more than simply indexing; they may hold values from the iterable itself, or could represent a more meaningful concept in the current context.

Second, using i as a loop variable name can reduce code readability and maintainability. When i takes on values directly from a list (as in for i in [2, 4, 6, 8]:), the variable is not an index but the actual item. A reader expecting i to be an index might assume i represents a position in a sequence, which leads to confusion when i is used to store the elements themselves. A more descriptive name like value, item, number, or even the plural values from the iterable can convey the intent more clearly.

Third, using single-letter names like i can contribute to ambiguity in more complex loops or nested structures. If there are inner loops or multiple iterables, single-letter variables can become easy to mismatch or misinterpret, increasing the likelihood of bugs or misread code. More descriptive identifiers promote self-documenting code.

Fourth, in some contexts, i is also used as a variable in mathematical expressions or in previous code blocks. Reusing i in a new loop without resetting or reusing it in a well-scoped way can lead to surprising results or side effects, especially if the loop variable remains in scope after the loop ends (depending on language and style conventions). A distinct, purpose-driven name helps mitigate this risk.

Fifth, if the iterable is a collection of numbers that are meaningful in their own right (e.g., error codes, IDs, or timestamps), naming the loop variable something descriptive (code, id, ts) preserves semantics and makes the code self-explanatory rather than implying indexing.

In summary, the core reasons i is discouraged as a loop variable name are readability, clarity about what the loop variable represents (index vs. value), and the potential for confusion in nested or more complex code. Replacing it with a more descriptive name aligns with common style guides and improves maintainability.

If an answer option were provided, a correct choice would likely emphasize one or more of these points: that i can be misleading (it is often an index but here holds values), that single-letter names are less descriptive, and that using descriptive identifiers enhances readability and reduces the chance of errors. An incorrect option might claim that using i is always an index, or that single-letter variables are universally acceptable, which would be misleading in the described context.

CS 1400-001 Spring 2025 Lab 10 Quiz

Given this code for i in [2, 4, 6, 8]: Why is i discouraged as a loop variable name?

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