Trouble with zip function in for loop; python

Question

Working in python 2.7.

I have two lists (simplified to make explanation more clear):

T = [[1, 0], [1, 0], [0, 5], [3, -1]]
B = [[1], [3], [2], [2]]

And three functions.

def exit_score(list):
    exit_scores = []
    length = len(list)
    for i in range(0, length):
        score = list[i][2] - list[i][0]
        exit_scores.append(score)
    return exit_scores

First I append the corresponding values of B to the corresponding lists in T:

def Trans(T, B):
    for t, b in zip(T, B):
        t.extend(b)
    a = exit_score(T)
    b = T
    score_add(b, a)

Then, using the previously listed exit_score function. I subtract the the value in the list[2] position from the value in the list[0] position fore each list. I then append those results to another list (exit_scores).

Finally, I want to add the exit_scores (now a), to the original list.

So I use my score_add(b, a) function which is:

score_add(team, exit_scores):
    for t, e in zip(team, exit_scores)
        t.extend(e)
    print team

If everything were working correctly, I would get an output like this:

[[1,0,1,0], [1,0,3,-2], [0,5,2,-2], [3,-1,2,1]]

Instead, I get a TypeError telling me that I can't iterate over an integer. But I've tried printing both a and b and both are in list form!

When I change the code to make sure that the exit scores are in a list:

def Trans(T, B):
    es = []
    for t, b in zip(T, B):
        t.extend(b)
    es.append(exit_score(T))
    score_add(T, es)

The entire exit_scores list (es) is added to the end of the first list of T:

[[1, 0, 1, 0, 2, 2, -1], [1, 0, 3], [0, 5, 2], [3, -1, 2]]

For the life of me, I can't figure out what I'm doing wrong...

You need to re-think all of that code. It's way more complex than it needs to be for a very simple operation. — agf
– agf, Commented Nov 3, 2011 at 17:17

Sven Marnach · Accepted Answer · 2011-11-03 17:25:24Z

4

This time it's list.append(), not list.extend():

def score_add(team, exit_scores):
    for t, e in zip(team, exit_scores)
        t.append(e)
    print team

B was a list of lists, while exit_scores is a list of integers.

Edit: Here is a cleaned-up version of the whole code:

for t, b in zip(T, B):
    t.extend(b)
    t.append(t[2] - t[0])

edited Nov 3, 2011 at 17:25

answered Nov 3, 2011 at 17:11

Sven Marnach

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2 Comments

Burton Guster Over a year ago

Right you are. Do you know I good resource where I can learn about these commands. Obviously, this area is a bit of a weakness...

Sven Marnach Over a year ago

@BurtonGuster: I'd start with some Python tutorial. The offficial tutorial is quite good, and I also like How to Think Like a Computer Scientist.

Austin Marshall · Accepted Answer · 2011-11-03 19:10:19Z

0

I'll bite:

map(lambda x, y: x + y + [x[0] - y[0]], T, B)

Yielding:

[[1, 0, 1, 0], [1, 0, 3, -2], [0, 5, 2, -2], [3, -1, 2, 1]]

Also, it can be done in a list comprehension:

[x+y+[x[0]-y[0]] for x, y in zip(T, B)]

edited Nov 3, 2011 at 19:10

answered Nov 3, 2011 at 17:53

Austin Marshall

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1 Comment

Sven Marnach Over a year ago

You've reproduced the result the OP didn't want.

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