Advanced Conditional Judgment: Multi-condition Application of Python if-elif-else

This article introduces the core structure `if-elif-else` for handling multi-condition branching in Python. When different logic needs to be executed based on multiple conditions, a single `if` statement is insufficient, and this structure is required. The syntax format is: `if condition1: ... elif condition2: ... else: ...`. Key points include: a colon must follow each condition, code blocks must be indented, there can be multiple `elif` clauses, there is only one `else` (placed at the end), and conditions are evaluated from top to bottom. Once a condition is met, the corresponding code block is executed, and subsequent conditions are not checked. A basic example uses score grading: for a score of 85, the conditions `>=90` (not met) and `>=80` (met) are evaluated in sequence, outputting "Grade: B". For advanced usage, note the condition order: they must be arranged from "strict to loose"; otherwise, later conditions will be ineffective. For example, in an incorrect example where `>=70` is checked first (satisfied by 85, outputting "C"), the `>=80` condition becomes invalid. This differs from multiple independent `if` statements: `elif` only executes the first met condition, avoiding duplicate outputs. Common errors include forgetting colons, incorrect indentation, reversing condition order, and omitting `else`. Mastering `if-elif-else` enables efficient handling of branching scenarios and is a fundamental component of Python programming.