Python：读取文字，readlines（）与iter（）

Question

I have a text file, with blocks of text, each separated by a line break. There are M blocks, each with N lines of text. I now want to read n lines for each of m blocks, where n<=N and m<=M .

I have tried something similar to the following:

num_blocks = 4 # or whatever value I choose
num_lines = 3 # or whatever value I choose

with open('file.txt', 'r') as f:
    lines = f.readlines()
    block_num = 0
    line_num = 0
    for line in lines:
        # do something with the line .....
        line_num += 1
        # has the specified number of lines been read?
        if line_num == num_lines:
            block_num += 1
            # has the specified number of blocks been read?
            if block_num == num_blocks:
                break;
            else:
                line_num = 0

However, when n<N , I need to skip over the remaining lines in the current block. I have tried putting

if line != '\n':
    continue

next to # do something with the line ..... , but this then skips the entire first block.

Alternatively, I have tried creating an iterator it = lines.iter() and incrementing each one accordingly. The problem with this approach is that there is no way of knowing when the end of the file has been reached. readlines() does this for me, but I don't know how to know when the last line has been reached if I am using an interator.

Any help? Thanks!

Answer 1

You can test for the end of an iterator like so:

try:
    it.next()
except StopIteration:
    *do something*

The StopIteration Exception is what an iterator throws when there is nothing left to iterate.