如何在一个被分割的文件中分割成多个部分？

Question

我有这样一个数据文件：

# coating file for detector A/R
# column 1 is the angle of incidence (degrees)
# column 2 is the wavelength (microns)
# column 3 is the transmission probability
# column 4 is the reflection probability
      14.2000     0.531000    0.0618000     0.938200
      14.2000     0.532000    0.0790500     0.920950
      14.2000     0.533000    0.0998900     0.900110
# it has lots of other lines
# datafile can be obtained from pastebin

到输入数据文件的链接是： http://pastebin.com/NaNbEm3E

我喜欢从这个输入创建20个文件，这样每个文件都有注释行。你知道吗

即：

#out1.txt
#comments
   first part of one-twentieth data

# out2.txt
# given comments
   second part of one-twentieth data

# and so on upto out20.txt

我们如何在python中这样做？你知道吗

我最初的尝试是这样的：

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author    : Bhishan Poudel
# Date      : May 23, 2016


# Imports
from __future__ import print_function
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

# read in comments from the file
infile = 'filecopy_multiple.txt'
outfile = 'comments.txt'
comments = []
with open(infile, 'r') as fi, open (outfile, 'a') as fo:
    for line in fi.readlines():
        if line.startswith('#'):
            comments.append(line)
            print(line)
            fo.write(line)


#==============================================================================
# read in a file
#
infile = infile
colnames = ['angle', 'wave','trans','refl']
print('{} {} {} {}'.format('\nreading file : ', infile, '','' ))
df = pd.read_csv(infile,sep='\s+', header = None,skiprows = 0,
                 comment='#',names=colnames,usecols=(0,1,2,3))
print('{} {} {} {}'.format('length of df : ', len(df),'',''))


# write 20 files
df = df
nfiles = 20
nrows = int(len(df)/nfiles)
groups = df.groupby(   np.arange(len(df.index)) / nrows   )
for (frameno, frame) in groups:
    frame.to_csv("output_%s.csv" % frameno,index=None, header=None,sep='\t')

到现在为止，我有20个分开的文件。我只想把注释行复制到每个文件中。但问题是：how to do so?

使用另一种方法创建20个注释，应该比只添加20个注释更容易。你知道吗

以下是一些有用的链接：
How to split a dataframe column into multiple columns
How to split a DataFrame column in python
Split a large pandas dataframe

Answer 1

应该这样做

# Store comments in this to use for all files
comments = []

# Create a new sub list for each of the 20 files
data = []
for _ in range(20):
    data.append([])

# Track line number
index = 0

# open input file
with open('input.txt', 'r') as fi:
    # fetch all lines at once so I can count them.
    lines = fi.readlines()

    # Loop to gather initial comments
    line = lines[index]
    while line.split()[0] == '#':
        comments.append(line)
        index += 1
        line = lines[index]

    # Calculate how many lines of data
    numdata = len(lines) - len(comments)

    for i in range(index, len(lines)):
        # Calculate which of the 20 files I'm working with
        filenum = (i - index) * 20 / numdata
        # Append line to appropriately tracked sub list
        data[filenum].append(lines[i])

for i in range(1, len(data) + 1):
    # Open output file
    with open('output{}.txt'.format(i), 'w') as fo:
        # Write comments
        for c in comments:
            fo.write(c)
        # Write data
        for line in data[i-1]:
            fo.write(line)

Answer 2

更新：优化代码

fn = r'D:\download\input.txt'

with open(fn, 'r') as f:
    data = f.readlines()

comments_lines = 0
for line in data:
    if line.strip().startswith('#'):
        comments_lines += 1
    else:
        break

nfiles = 20
chunk_size = (len(data)-comments_lines)//nfiles

for i in range(nfiles):
    with open('d:/temp/output_{:02d}.txt'.format(i), 'w') as f:
        f.write(''.join(data[:comments_lines] + data[comments_lines+i*chunk_size:comments_lines+(i+1)*chunk_size]))
        if i == nfiles - 1 and len(data) > comments_lines+(i+1)*chunk_size:
            f.write(''.join(data[comments_lines+(i+1)*chunk_size:]))

原始答案：

comments = []
data = []

with open('input.txt', 'r') as f:
    data = f.readlines()

i = 0
for line in data:
        if line.strip().startswith('#'):
            comments.append(line)
            i += 1
        else:
            break

data[:] = data[i:]

i=0
for x in range(0, len(data), len(data)//20):
    with open('output_{:02d}.txt'.format(i), 'w') as f:
        f.write(''.join(comments + data[x:x+20]))
        i += 1