Exploring mammoth text data in Python

Question

Exploring mammoth text data in Python

I am currently diving into Python development with my first project, which involves parsing a hefty 2GB file. After discovering that processing it line by line would be agonizingly slow, I decided to opt for the buffering method. Here's what I'm using:

f = open(filename)                  
lines = 0
buf_size = 1024 * 1024
read_f = f.read 
buf = read_f(buf_size)
while buf:
    for line in buf:
      #code for string search
      print line
    buf = read_f(buf_size)

However, I've encountered an issue where the "print line" statement does not actually print a full line; instead, it displays one character at a time per line. This is causing trouble when attempting substring searches on the data. Can anyone offer assistance?

python parsing search find large-files

Answer 1

Answer №1

display line showcases a character due to buf being a string, leading to the characters of the string being yielded as 1-character strings.

If you found reading line-by-line to be slow, how exactly did you go about implementing the read? Using readlines() could explain the sluggishness (refer to ).

Files can be iterated over their lines, and Python automatically selects a buffer size during iteration, which may align with your requirements:

for line in f:
    # perform search operations

If you prefer to specify the buffer size manually, you could approach it like this:

buf = f.readlines(buffersize)
while buf:
    for line in buf:
        # perform search operations
    buf = f.readlines(buffersize)

Generally speaking, the first approach is typically more efficient.

Answer 2

display line showcases a character due to buf being a string, leading to the characters of the string being yielded as 1-character strings.

If you found reading line-by-line to be slow, how exactly did you go about implementing the read? Using readlines() could explain the sluggishness (refer to ).

Files can be iterated over their lines, and Python automatically selects a buffer size during iteration, which may align with your requirements:

for line in f:
    # perform search operations

If you prefer to specify the buffer size manually, you could approach it like this:

buf = f.readlines(buffersize)
while buf:
    for line in buf:
        # perform search operations
    buf = f.readlines(buffersize)

Generally speaking, the first approach is typically more efficient.

Answer 3

Answer №2

The issue here is that 'buf' is being treated as a string.

Let's assume buf = "abcd"

So, buf[0] would equal 'a', buf[1] would equal 'b', and so on.

for char in buf:
    print(char)

This code snippet will output: a b c d

Just keep in mind that your loop is iterating over characters of the buffer string, not separate lines. To fix this, you can either use the readlines method or split your buffer into individual lines by searching for "\n".

Answer 4

The issue here is that 'buf' is being treated as a string.

Let's assume buf = "abcd"

So, buf[0] would equal 'a', buf[1] would equal 'b', and so on.

for char in buf:
    print(char)

This code snippet will output: a b c d

Just keep in mind that your loop is iterating over characters of the buffer string, not separate lines. To fix this, you can either use the readlines method or split your buffer into individual lines by searching for "\n".

Exploring mammoth text data in Python

Answer №1

Answer №2

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