What is the most efficient way to get first and last line of a text file?

user_403709 0
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I have a text file which contains a time stamp on each line. My goal is to find the time range. All the times are in order so the first line will be the earliest time and the last line will be the latest time. I only need the very first and very last line. What would be the most efficient way to get these lines in python?

Note: These files are relatively large in length, about 1-2 million lines each and I have to do this for several hundred files.

seek file python
12 Answers

Nobody mentioned using reversed:

f=open(file,"r")
r=reversed(f.readlines())
last_line_of_file = r.next()
user_95123020 
with open(filename, "rb") as f:#Needs to be in binary mode for the seek from the end to work
    first = f.readline()
    if f.read(1) == '':
        return first
    f.seek(-2, 2)  # Jump to the second last byte.
    while f.read(1) != b"\n":  # Until EOL is found...
        f.seek(-2, 1)  # ...jump back the read byte plus one more.
    last = f.readline()  # Read last line.
    return last

The above answer is a modified version of the above answers which handles the case that there is only one line in the file

user_37013770
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