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Skipping to a Specific Line in a Large Text File
When dealing with massive text files, it's common to encounter the need to jump directly to a particular line. One straightforward approach involves iteratively reading through the file, but this can be inefficient if you know the target line number in advance.
The Problem:
Using the code snippet provided:
startFromLine = 141978 urlsfile = open(filename, "rb", 0) linesCounter = 1 for line in urlsfile: if linesCounter > startFromLine: DoSomethingWithThisLine(line) linesCounter += 1
This code reads the file line by line, requiring processing of all preceding lines, even though they are irrelevant.
A More Efficient Solution:
To efficiently jump to a specific line, you can utilize a two-step approach:
Build an Offset List:
Seek to Target Line:
Here is an example:
line_offset = [] offset = 0 for line in file: line_offset.append(offset) offset += len(line) file.seek(0) target_line = 141978 file.seek(line_offset[target_line])
This approach allows you to skip directly to the desired line, avoiding the unnecessary overhead of processing irrelevant lines.
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