Python-如何从文件中删除列

Question

I'd like to remove the first column from a file. The file contains 3 columns separated by space and the columns has the following titles: X', 'Displacement' and 'Force' (Please see the image).

I have came up with the following code, but to my disappointment it doesn't work!

f = open("datafile.txt", 'w')
 for line in f:
  line = line.split()
  del x[0]
f.close()

Any help is much appreciated ! Esan

Answer 1

First of all, you're attempting to read from a file (by iterating through the file contents) that is open for writing. This will give you an IOError .

Second, there is no variable named x in existence (you have not declared/set one in the script). This will generate a NameError .

Thirdly and finally, once you have finished (correctly) reading and editing the columns in your file, you will need to write the data back into the file.

To avoid loading a (potentially large) file into memory all at once, it is probably a good idea to read from one file (line by line) and write to a new file simultaneously.

Something like this might work:

f = open("datafile.txt", "r")
g = open("datafile_fixed.txt", "w")

for line in f:
    if line.strip():
        g.write("\t".join(line.split()[1:]) + "\n")

f.close()
g.close()

Answer 2

print ''.join([' '.join(l.split()[1:]) for l in file('datafile.txt')])

或者，如果您想保留空格并且知道第二列始终以第10个字符开头：

print ''.join([l[11:] for l in file('datafile.txt')])

Answer 3

Some reading about python i/o might be helpful, but something like the following should get you on your feet:

with open("datafile.txt", "r") as fin:
    with open("outputfile.txt", "w") as fout:
        for line in fin:
            line = line.split(' ')
            if len(line) == 3:
                del line[0]
                fout.write(line[0] + ' ' + line[1])
            else:
                fout.write('\n')

EDIT: fixed to work with blank lines