Python fastest way to read a large text file (several GB) [duplicate]

Question

This question already has an answer here:

• How to read a large file line by line 10 answers

i have a large text file (~7 GB). I am looking if exist the fastest way to read large text file. I have been reading about using several approach as read chunk-by-chunk in order to speed the process.

at example effbot suggest

# File: readline-example-3.py

file = open("sample.txt")

while 1:
    lines = file.readlines(100000)
    if not lines:
        break
    for line in lines:
        pass # do something**strong text**

in order to process 96,900 lines of text per second. Other authors suggest to use islice()

from itertools import islice

with open(...) as f:
    while True:
        next_n_lines = list(islice(f, n))
        if not next_n_lines:
            break
        # process next_n_lines

list(islice(f, n)) will return a list of the next n lines of the file f. Using this inside a loop will give you the file in chunks of n lines

Answer 1

with open(<FILE>) as FileObj:
    for lines in FileObj:
        print lines # or do some other thing with the line...

will read one line at the time to memory, and close the file when done...