Triple for loop for a data set

Question

I am writing a triple for loop in Python. Since the data set is larger, it takes more than 1.5 hours to finish. Is there any fast way to avoid the loop?

idx = []
for key, value in bid_img.iteritems():
    for v in value:
        loc = 0
        for pid in pid_lst:
            loc += 1
            if v == pid:
                idx.append(loc)

---

What I have:

1. bid_img a dictionary that contain multiple values per key.
2. pid_lst a list.

I want to index items for values in dic, if they match with list provided, then store them in idx and loc for index.

Sample input:

bid_img = {'123': ['4123','12312','1231234'], '2312':['413','112','12334']}; 

Sample output:

idx = [5, 11,62, 32]

1. The input is larger than \$10^6\$.
2. The order of output is very important; I want the exact order.
3. I want to find the index or location (for each value in dict) in list pid_lst.

Answer 1

First, the outer loop can be optimised. You're using

for key, value in bid_img.iteritems():

But key is unused. Suggestion:

for value in bid_img.itervalues():

The inner loop can be optimised as well:

    loc = 0
    for pid in pid_lst:
        loc += 1
        if v == pid:
            idx.append(loc)

Suggestion:

    for loc, pid in enumerate(pid_lst, start=1):
        if v == pid:
            idx.append(loc)

The repeated calls to idx.append can be costly. Why not:

    idx.extend(loc for loc, pid in enumerate(pid_lst, start=1) if v == pid)

(Hope I didn't make any typo's, typing from my phone)