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pythondata-mininglarge-data

Read specific number of lines in python

I have the BIG data text file for example:

#01textline1
1 2 3 4 5 6
2 3 5 6 7 3
3 5 6 7 6 4
4 6 7 8 9 9

1 2 3 6 4 7
3 5 7 7 8 4
4 6 6 7 8 5

3 4 5 6 7 8
4 6 7 8 8 9
..
..
Solution

  • You do not need a loop to accomplish your purpose. Just use the index function on the list to get the index of the two lines and take all the lines between them.

    Note that I changed your file.readlines() to strip trailing newlines.

    (Using file.read().splitlines() can fail, if read() ends in the middle of a line of data.)

    file1 = open("data.txt","r")
file2=open("newdata.txt","w")
lines = [ line.rstrip() for line in file1.readlines() ]

firstIndex = lines.index("#02textline2")
secondIndex = lines.index("#03textline3")

print firstIndex, secondIndex
file2.write("\n".join(lines[firstIndex  + 1 : secondIndex]))


file1.close()
file2.close()