将选定的列从一个文件复制到另一个

Question

I want to read all columns from the input file and print only selected columns to the output file (0th, 3rd and 2nd column), preserving the header ( 4 and Temperature = 298 K ).

My current code writes "[1.0, 1.0]" to output file. How can I fix it?

#!/usr/bin/python

with open("test.txt", "r") as f:
    a1=[]
    a2=[]
    a3=[]
    a4=[]
    for line in f:
        if not line.strip() or line.startswith('Temperature') or line.startswith('4'): continue
        row = line.split()
        a1.append(str(row[0]))
        a2.append(float(row[1]))
        a3.append(float(row[2]))
        a4.append(float(row[3]))
f = open('output.txt','a')
f.write(str(a1)+str(a3)+str(a2)) 
f.close()

Input file:

4
Temperature = 298 K
C   -5.27210   0.23153   0.13488 
H   -1.99335  -2.87058   3.25594 
H   -1.33502  -3.88407   1.93295 
H   -3.06617  -3.39783   1.91314 

Requested output:

4
Temperature = 298 K
C   0.13488   0.23153    
H   3.25594  -2.87058    
H   1.93295  -3.88407   
H   1.91314  -3.39783   

Answer 1

I don't quite get why you use four different lists there... You could do it with just one container, like this (not tested):

#!/usr/bin/python

newlines = []
with open("test.txt", "r") as f:
    for line in f:
        if not line.strip() or line.startswith('Temperature') or line.startswith('4'): continue
        row = line.split()
        newlines.append('   '.join([row[0], row[3], row[2]]))

f = open('output.txt','a')
f.write('\n'.join(newlines))
f.close()

Answer 2

How about that?

with open('data.txt', 'r') as fin:
    with open('data2.txt', 'w') as fout:
        # Header
        fout.write(fin.readline())
        fout.write(fin.readline())
        # Columns
        for l in fin:
            cols = l.split()
            fout.write("%s  % f  % f\n" % (cols[0], float(cols[3]), float(cols[2])))

The code stores only one line of the file at a time and writes to the output file immediately. Also, the spacing is preserved as in the original file.