OSError: Too Many Open Files

Why This Happens

Each open file, socket, or pipe consumes a file descriptor. Operating systems limit the number per process. If you open files in a loop without closing them, you exhaust the limit.

The Problem

files = []
for name in filenames:
    f = open(name)
    files.append(f.read())

The Fix

files = []
for name in filenames:
    with open(name) as f:
        files.append(f.read())

Step-by-Step Fix

1. 1

   Use with statements

   Always use 'with open(path) as f:' for auto-close.

2. 2

   Close resources explicitly

   Call .close() in a finally block.

3. 3

   Increase the limit

   Run ulimit -n 4096 to increase the limit.