I asked this question here in Stackoverlow View the last 5 lines of a file with PHP?
Now I would like to know how I could do the same thing in Python.
How could I get the last 5 lines of a large file, without having to fully load it into memory in Python?
The most elegant solution I found (among the many that exist) is this:
def tail(f, n):
assert n >= 0
pos, lines = n+1, []
while len(lines) <= n:
try:
f.seek(-pos, 2)
except IOError:
f.seek(0)
break
finally:
lines = list(f)
pos *= 2
return lines[-n:]
My suggestion includes using an iterator with for...in . This uses relatively little memory and remains quite legible, in my opinion.
def tail_file(file_name, number):
lines = []
with open(file_name) as f:
for line in f:
lines.append(line.rstrip())
if len(lines) > number:
lines.pop(0)
return lines