第306页 | Learning Python | 阅读 ‧ 电子书库

while Loops

Python’s while statement is the most general iteration construct in the language. In simple terms, it repeatedly executes a block of (normally indented) statements as long as a test at the top keeps evaluating to a true value. It is called a “loop” because control keeps looping back to the start of the statement until the test becomes false. When the test becomes false, control passes to the statement that follows the while block. The net effect is that the loop’s body is executed repeatedly while the test at the top is true; if the test is false to begin with, the body never runs.