Python-Risk of variable iteration objects in the for loop Risk in FOR loop while looping mutable iterable object, loopingmutable

Python-Risk of variable iteration objects in the for loop Risk in FOR loop while looping mutable iterable object, loopingmutable

>>> A = [1, 2, 4, 5, 6] >>> for item in :... a. remove (item)... >>> a [2, 4, 6]

Is it strange to see the above Code? Intuitively, we just want to delete each element in queue a in sequence. Why is the final result true [2, 4, 6]? If you are smart enough, you must guess why. For each for loop, the current. after the remove (item) operation is complete, the-phase pair is shortened; the elements after the item are added to the previously deleted position, so that the next element is deleted in this for loop. It can be seen that if our iteration object changes in the loop body, using the for statement will bring unpredictable risks.

 

>>> A = [1, 2, 4, 5, 6] >>> for item in :... print ('index: ',. index (item), 'content: ', item )... a. remove (item )... index: 0 Content: 1 Index: 1 Content: 3 Index: 2 Content: 5 >>> a [2, 4, 6]