How to optimize this program in Python?

I have one file with indexes. In example, they are:

1    Fruit
2    Meat
3    Fish        
4    Salmon
5    Pork
6    Apple

And a dictionary, because I want to match entries that I choose, so for example

similar = {'1' : '6', '2' : '5'}

Since they are on the same file, what my program does is, IE, scans for the '1' on the file, and then re-scans from the beginning looking for the '6'. Same with all the numbers, re-scanning always.

It's a very large file with a lot of numbers.

This is some code

similar = { '4719' : '4720c01' }

for aline in invFormatted:
    lines = aline.split("\t") #Splits the CSV file on every tab.
    lotID = lines[0]
    partNO = lines[1] #Splits and gets the part that would be the "index"
    if similar.has_key(partNO):
        for alines in invFormatted:
            liness = alines.split("\t")
            lotIDmatch = liness[0]
            partNOmatch = liness[1]
            if liness[1] == similar[partNO]:

Would there be a way to make it so it only scans it once?

Or any other ideas to put better this program?

Cheers!

In fear of falling in the TL;DR category or the "you want me to do this code for you" category, I didn't post the full thing, but since some people asked, here it is (don't kill me).

There is a text file formatted this way.

51689299    4719    Medium Azure    Riding Cycle
51689345    4720c01 Trans-Clear Wheel & Tire Assembly

In real life, it would have thousands of entries.

Then, my python file 'knows' that the part number 4719 matches the part number 4720c01.

similar = { '4719' : '4720c01' }

Now, what it does. (I think!)

invFormatted = open('export.txt', 'r') #Opens the file with the part numbers

with open ('upload.txt', 'a') as upload:

    upload.write("<INVENTORY>") #Something that would be on the export

    for aline in invFormatted:
        lines = aline.split("\t") #Splits the text file on every tab
        lotID = lines[0] #The lot ID is the first word
        partNO = lines[1] #Part number the second one
        if partNO in similar: #Sees if the part number in question has a match, if YES
            for alines in invFormatted: #Searchs my inventory file again to see if the match is in my inventory
                liness = alines.split("\t")
                lotIDmatch = liness[0]
                partNOmatch = liness[1]
                if liness[1] == similar[partNO]: #if YES, prints out what I want it to print, and goes back to the first step
                    upload.write("blabla")

    invFormatted.close()

    upload.write("\n</INVENTORY>")

There it is, thank you!

I have gotten here so far, I think it's close to as much optimization as I can. Maybe someone can think of else?

parts = {}

infile = open("export.txt")
for line in infile:
    line = line.strip()
    xml = [p.strip() for p in line.split("\t")]
    parts[xml[1]] = (xml[0], xml[2], xml[3])

for aline in invFormatted:
    lines = aline.split("\t") #Splits the CSV file on every "
    lotID = lines[0]
    partNO = lines[1]
    if partNO in similar:
        similarPart = similar[partNO]
        if partNO in parts:
                upload.write("\n <ITEM>\n  <LOTID>" + lotID + "</LOTID>\n  <DESCRIPTION>To be used with &amp;lt;a href=\"/storeDetail.asp?b=-16205034&amp;h=314137&amp;q=" + similarPart + "\"&amp;gt;" + similarPart + "&amp;lt;/a&amp;gt;</DESCRIPTION>\n" + " </ITEM>")