如何在Python中合并来自不同txt文件的一些列数据？

Question

I have some txt files, which need to extract certain columns out and store in one txt file.

a1.txt:

53, 42
54, 38
55, 37
57, 48

b1.txt:

45, 15, 30, 2
16, 59, 31, 4
87, 09, 32, 5
58, 16, 33, 3

what i need is c.txt (add the last column of b1.txt to the a1.txt):

53, 42, 2
54, 38, 4
55, 37, 5
57, 48, 3

the 4th column of b.txt should be added to the 5th column of a.txt . Then create a new file c.txt . I try some code, but it did not work. cmd said "TypeError: list indice must be integers, not srt" . I have no idea how to merge the columns from different files together. Hopefully someone could help me to revise the code. Thank you so much!

def readf(filename):
    lines=file(filename).readlines()
    for i in lines:
        data=i.split()
    return data

fa=readf('a1.txt')
fb=readf('b1.txt')

lines=[]
for i in fa:
    s=fa[i]+fb[3]
    s+='\n'
    lines.append(s)

with open ('c.txt','w') as f:
    f.writelines(lines)
    f.close>

Answer 1

In the following command you have passed a string as the index to a list :

for i in fa:
    s=fa[i]+fb[3]

Note that you are iterating over a file object!

but as a better way for such problems i suggest the csv module.

from itertools import izip_longest
import csv
with open('a1.txt', 'rb') as csv1,open('b1.txt', 'rb') as csv2,open('c.txt', 'w') as out:
     spam1 = csv.reader(csv1, delimiter=',')
     spam2 = csv.reader(csv2, delimiter=',')
     last_column=list(izip_longest(*spam2))[-1]
     for i,j in  izip_longest(spam1,last_column):
        out.write(','.join([t.strip(';') for t in i])+','+j+'\n')

Here last_column=list(izip_longest(*spam2))[-1] will gave you the last column of b1.txt and izip_longest(spam1,last_column) will gave you the following list :

[(['53', ' 42;'], ' 2;'), (['54', ' 38;'], ' 4;'), (['55', ' 37;'], ' 5;'), (['57', ' 48; '], ' 3;')]

So you can strip the elements with ; and write to file.

If ; can be ignored you can change the last line to :

out.write(','.join(i)+','+j+'\n')

Answer 2

Since you need to split your text using , and ; as parameters, you can use re to accomplish the job. Then is just a matter or writing all the attributes of the first file and the last attribute of the second file.

import re
with open("a.txt", 'r') as f:
    a1 = [re.findall(r"[\w']+", line) for line in f]
with open("b.txt", 'r') as b:
    b1 = [re.findall(r"[\w']+", line) for line in b]
with open("c.txt", 'w') as c:
    for x,y in zip(a1,b1):
        c.write("{},{}\n".format(",".join(x),y[-1]))  

This creates file c which looks like

53,42,2 
54,38,4 
55,37,5 
57,48,3

Answer 3

How about you use pandas:

import pandas as pd
a1 = pd.read_csv('a1.txt', header= None ,escapechar=';')
b1 = pd.read_csv('b1.txt', header= None)

a1[2] = b1[3]

a1.to_csv('c.txt',index=False,header= False)

c.txt:

53, 42, 2;
54, 38, 4;
55, 37, 5;
57, 48, 3;

Answer 4

def read_file(file_name):
    col_data = []
    with open(file_name) as data_file:
        for data in data_file.readlines():
            col1, col2, col3, col4 = data.split(",")
            col_data.append(col4[:-1])
    return col_data

numbers = read_file("b1.txt")

with open("a1.txt") as a_file:
    with open("new_file.txt", "w") as new_file:
        lines = a_file.readlines()
        for line in xrange(len(lines)):
            new_file.write(lines[line][:-1] + " ,"+numbers[line]+"\n")