Question

I’m a beginner in Python and have a file i’ve read in that has an Market_ID field. While looping over this file (list), I need to access the Market_name in a 2nd file (Market_ID,Market_Name).

What’s the best place for me to start? I can give more detail on what the program is doing if necessary.

The files(lists) are laid out as follows:

File1:  Cust_ID, Market_ID, Cust_Name, IsNew
File2:  Market_ID, Market_Name

My main loop is over File1. I need to be able to access the Market_Name from File2 to be able to place it in a new file i’m creating from data in File1. Hope that helps.

Answer 1

If the files are not too big (a few megabytes) you could store each item in a dict() using the Market_ID as key.

This looks like data drom a database – if you are familiar with
relational databases and their use you could insert each file into a
separate table and then perform queries. Python has an interface to
sqlite in its standard library.

For solving this quickly I suggest to use dicts though.
BY — sleeplessnerd

More about dictionaries,
More about sqlite

file2 = open("/path/to/file2", "r")
market_names = {}
for line in file2:
  fields = line.split(",")
  market_names[int(fields[0])] = fields[1]
file2.close()

file1 = open("/path/to/file1", "r")
for line in file1:
  fields = line.split(",")
  market_name = market_names[int(fields[1])]
  # do what ever you want with the Market_Name associated with
  # the Market_ID contained in this line
file1.close()