如何从python中的.txt文件读取特定行？

Question

I know I can read the line by line with

dataFile = open('myfile.txt', 'r')
firstLine = dataFile.readline()
secondLine = dataFile.readline()
...

I also know how to read all the lines in one go

dataFile = open('myfile.txt', 'r')
allLines =  dataFile.read()

But my question is how to read one particular line from .txt file?

I wish to read that line by its index.

eg I want the 4th line, I expect something like

dataFile = open('myfile.txt', 'r')
allLines =  dataFile.readLineByIndex(3)

Answer 1

Skip 3 lines:

with open('myfile.txt', 'r') as dataFile:
    for i in range(3):
        next(dataFile)
    the_4th_line = next(dataFile)

Or use linecache.getline :

the_4th_line = linecache.getline('myfile.txt', 4)

Answer 2

From another Ans

Use Python Standard Library's linecache module:

line = linecache.getline(thefilename, 33)
should do exactly what you want. You don't even need to open the file -- linecache does it all for you!

Answer 3

You can do exactly as you wanted with this:

DataFile = open('mytext.txt', 'r')

content = DataFile.readlines()

oneline = content[5]

DataFile.close()

you could take this down to three lines by removing oneline = content[5] and using content[5] without creating another variable ( print(content[5]) for example) I did this just to make it clear that content[5] must be a used as a list to read the one line.