WTF: Enumeration Galore

 I found some Python code from a guy that used lots of enumeration. He probably copied the code from somewhere and did not understand it well. At the end, we have some pretty confusing code. For example, he wanted to add to a list of trusting accounts some accounts from another list, avoiding duplication. Here is his code:

for i, index in enumerate(account_list):

    if len([a for a in trusting_accounts if a == account_list[i]]) == 0:

        trusting_accounts += [account_list[i]]

The enumerate function returns both the index and the item in the list. However, the fact that he named them i and index shows me that he had no idea what the second part was about. He actually never used it, always referring to the index confusingly called 'i'.

The if condition is even more confusing. It triggers only if the list of accounts having the same name as the current account in the loop is empty. Simply said, it triggers if the account is not already in the list. The corrected version of the code is here:

for account in account_list:

    if account not in trusting_accounts:

        trusting_accounts.append(account)

Of course, this pattern was used in a lots of place in his code. The function for removing a list of accounts from the trusting accounts for instance looks like this:

for i, index in enumerate(account_list):

    for ii, iindex in enumerate(trusting_accounts):

        if account_list[i] == trusting_accounts[ii]:

            trusting_accounts.pop(ii)

There is an inner enumeration to find the index of the account to remove. He probably didn't know that there is a remove function in the list doing all the work. Here is the corrected code:

for account in account_list:

    if account in trusting_accounts:

        trusting_accounts.remove(account)

Much clearer...