In the Code Style chapter examples - Short Ways to Manipulate Lists there is an example "Add three to all list members."

"bad"

for i in range(len(a)):
    a[i] += 3

"good"

a = [i + 3 for i in a]

Unfortunately the "bad" and "good" examples do a different things:

• "bad" modifies the original list in place
• "good" creates a new modified list and does not change the original object - not exactly "Add three to all list members."

Although the "good" code looks cleaner the result could be unwanted for example in case of huge lists or required side-effect of modifying the original list. The code at least needs an explanation.