Use readline to read txt file python3

Question

I been working on this for hours and I cant get it right, any help would be appreciated! My question is how do I use the function .readline() to read until the end of a text file? I know that .readlines() work as well but I'm trying to process one line at a time.

Here's what I have for my code so far:

    a = open("SampleTxt.txt","r")

    While True:

        a.readline()

My problem is that I get an infinite loop when I run this, shouldn't it have stopped once it couldn't read a line any more?

score 35 · Answer 1 · answered Mar 09 '15 at 06:16

35

a.readline() will return '' an empty string when no more data is available, you need to check that and then break your while, eg:

while True:
    line = a.readline()
    if not line: 
        break

If it's not purely for learning purposes then you really should be using a with statement and for-loop to process the file, line by line:

with open('SampleTxt.txt') as fin:
    for line in fin:
        pass # do something

It's more clear as to your intent, and by using the with block, the fileobj will be released on an exception or when the block ends.

answered Mar 09 '15 at 06:16

Jon Clements

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2

The second method still reads the file line by line and does not load the whole file into memory, right? – krackoder Nov 14 '19 at 07:24
@nishant yes that better/efficient memory usage – Walid Dec 31 '20 at 00:36

Use readline to read txt file python3

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