Reset Read or Write position in a file with Python with seek()
This is something I used to stumble on a lot in the early days of my Python coding adventure so I thought to write a quick article about it.
Python Open file
Opening a file for read or write in Python can be achieved with the following code:
# Open file file = open("/Python/Files/MyFile.txt")
Python Read file
To read content of the file we simply use the read() method
# Read file to the end of file file.read() 'This is the first line\nAnd a second\nAnd even a third\nShall we put a fourth?\nWhy not a fifth\nOr a sixt\n'
Note that Python will print the newline character and will not split lines for you (but that’s material for another day/post)
Where is my text?
Say you want to print again file content issue the same command again will leave you with something like this
# Read file again file.read() ''
Not a lot to see on screen, so where did our file’s content go?
When python reads a file’s content it will move file current position to the end of the file so trying to re-read it again will yield the above result. Nothing as there is nothing else to read.
You can easily go back to the beginning of the file with the seek() method which is used like this:
# Go back to position 0 # Or beginning of file file.seek(0, 0)
Syntax of seek() method fileObject.seek(offset[, whence])
offset is the position of the read/write pointer within the file.
whence is optional and defaults to 0 which means absolute file positioning, other possible values are 1 which means seek relative to the current position and 2 which means seek relative to the file’s end
Now if you try to read the file again all content will be correctly displayed
file.read() 'This is the first line\nAnd a second\nAnd even a third\nShall we put a fourth?\nWhy not a fifth\nOr a sixt\n'