Is Python a

Why You Will Care: Emulating C while LoopsThe section on expression statements in Chapter 11 stated that Python doesn’t allowstatements such as assignments to appear in places where it expects an expression.That means this common C language coding pattern won’t work in Python:while ((x = next( )) != NULL) {...process x...}C assignments return the value assigned, but Python assignments are just statements,not expressions. This eliminates a notorious class of C errors (you can’t accidentallytype = in Python when you mean ==). But, if you need similar behavior, there are at leastthree ways to get the same effect in Python while loops without embedding assignmentsin loop tests. You can move the assignment into the loop body with a break:while True:x = next( )if not x: break...process x...or move the assignment into the loop with tests:x = 1while x:x = next( )if x:...process x...or move the first assignment outside the loop:x = next( )while x:...process x...x = next( )Of these three coding patterns, the first may be considered by some to be the leaststructured, but it also seems to be the simplest, and most commonly used. (A simplePython for loop may replace some C loops as well.)The for statement also supports an optional else block, which works exactly as itdoes in a while loop—it’s executed if the loop exits without running into a breakstatement (i.e., if all items in the sequence have been visited). The break and continuestatements introduced earlier also work the same in a for loop as they do in a while.The for loop’s complete format can be described this way:for in :if : breakif : continueelse:# Assign object items to target# Exit loop now, skip else# Go to top of loop now# If we didn't hit a 'break'for Loops | 255