Python：在包含模式行的模式后打印x行

Question

If a line starts with a number( xyz ) in a file, I need to print(or write to a file) this line and the next xyz+1 lines.
What's the best way to do this?

So far, I've been able to print the line that starts with an int . How do I print the next lines?

import glob, os, sys
import subprocess

file = 'filename.txt'
with open(file,'r') as f:
    data = f.readlines()
for line in data:
    if line[0].isdigit():
       print int(line)

If I made an iterator out of data , the print function skips a line every time.

with open(file,'r') as f:
   data = f.readlines()
x = iter(data)
for line in x:
    if line[0].isdigit():
       print int(line)
       for i in range(int(line)):
          print x.next()   

How could I make it stop skipping lines?

Answer 1

Use a flag, when you find the line set it to true, then use it to write all future lines:

can_write = False
with open('source.txt') as f, open('destination.txt', 'w') as fw:
    for line in f:
        if line.startswith(xyz):
            can_write = True
        if can_write:
            fw.write(line)