从文件打印第N个字符（第8个字符）[Python]

Question

I have a long sequence of bits that I dumped from a file. Now, I want to take this sequence of bits and be able to extract every 8th bit from it. For example:

100010010101000001001110010001110000110100001010
000110100000101000000000000000000000000000001101
010010010100100001000100010100100000000000000000
etc

would give:

100110
(extraction from second line)
(extraction from third line)
etc

I have the following code so far:

 #/usr/bin/python

 with open("thebits.txt", 'r') as f:
        content = [x.strip('\n') for x in f.readlines()]
        {//logic to extract every 8th bit from each line and print it}

How can I extract every 8th bit from each line? .

Answer 1

You can use simple slicing:

with open('thebits.txt', 'r') as f:
    for line in f:
        print line.strip()[7::8]

Your example file gives:

100110
000001
100000

The slice [7::8] gives you every 8th character starting from the 8th (7 indexed from 0).

Answer 2

with open(infile) as f:
    print("".join(line[7::8] for line in f))

Answer 3

Assuming you want each line separately:

with open('tmp.txt', 'r') as f:
    for line in f.read().splitlines():
        print(line[7::8])