python按规则合并文件

Question

I need to write script in python that accept and merge 2 files to a new file according to the following rule: 1)take 1 word from 1st file followed by 2 words from the second file. 2) when we reach the end of 1 file i'll need to copy the rest of the other file to the merged file without change.

I wrote that script, but i managed to only read 1 word from each file. Complete script will be nice, but I really want to understand by words how i can do this by my own.

This is what i wrote:

def exercise3(file1,file2):
    lstFile1=readFile(file1)
    lstFile2=readFile(file2)

    with open("mergedFile", 'w') as outfile:
        merged = [j for i in zip(lstFile1, lstFile2) for j in i]
        for word in merged:
            outfile.write(word)


def readFile(filename):
    lines = []
    with open(filename) as file:
        for line in file:
            line = line.strip()
            for word in line.split():
                lines.append(word)
    return lines

Answer 1

Your immediate problem is that zip alternates items from the iterables you give it: in short, it's a 1:1 mapping, where you need 1:2. Try this:

lstFile2a = listfile2[0::2]
lstFile2b = listfile2[1::2]
... zip(lstfile1, listfile2a, lstfile2b)

This is a bit inefficient, but gets the job done.

Another way is to zip up pairs (2-tuples) in lstFile2 before zipping it with lstFile1. A third way is to forget zipping altogether, and run your own indexing:

for i in min(len(lstFile1), len(lstFile2)//2):
    outfile.write(lstFile1[i])
    outfile.write(lstFile2[2*i])
    outfile.write(lstFile2[2*i+1])

However, this leaves you with the leftovers of the longer file to handle.

These aren't particularly elegant, but they should get you moving.