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Is there a Python file type for accessing random lines without traversing the whole file? I need to search within a large file, reading the whole thing into memory wouldn't be possible.
Any types or methods would be appreciated.
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Purpose of linecache module in Python's standard library is to facilitate random access to any text file, although this module is extensively used by Python's traceback module to generate error trace stack. Further prettyprints of reading are held in a cache so that it saves time while reading lines repeatedly.
Opening a File. You can open a file using the open() function. The open() function takes two arguments - filename and mode. There are different access modes in which you can open a file.
This seems like just the sort of thing mmap was designed for. A mmap object creates a string-like interface to a file:
>>> f = open("bonnie.txt", "wb")
>>> f.write("My Bonnie lies over the ocean.")
>>> f.close()
>>> f.open("bonnie.txt", "r+b")
>>> mm = mmap(f.fileno(), 0)
>>> print mm[3:9]
Bonnie
In case you were wondering, mmap objects can also be assigned to:
>>> print mm[24:]
ocean.
>>> mm[24:] = "sea. "
>>> print mm[:]
My Bonnie lies over the sea.
You can use linecache:
import linecache
print linecache.getline(your_file.txt, randomLineNumber) # Note: first line is 1, not 0
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