How to convert strings to integers in Python

Question

I have code that converts an integer into a string to write it into a file, but the code to convert it back into an integer so I can put it through simple equations doesn't work.

my code: writing:

saveposx = open("sevedposx.txt", "w")
saveposy = open("sevedposy.txt", "w")
saveposx.write(str(x))
saveposy.write(str(y))

where x = 32 and y = 32 as well

reading:

readposx = open("sevedposx.txt", "r")
readposy = open("sevedposy.txt", "r")
posx = readposx.read(50)
posy = readposy.read(50)
actposx = int(posx)
actposy = int(posy)
actpos = ((actposx - 2), (actposy - 2))

x and y are defined outside a loop as to allow rewriting of x and y .

My code gives me this error:

  File "name_yet_to_come.py", line 399, in <module>
    actposx = int(posx)
ValueError: invalid literal for int() with base 10: ''

Thanks

Answer 1

The error message indicates that the file is empty. Probably the output file variable is still referenced / in the scope, or was not garbage collected yet.

Use

with open(...) as f:
    pass # do something with f here

to have the file automatically flushed and closed at the end of the scope.

Or just close them explicitly with f.close() , but consider using a try finally block then.

You can open multiple files in this scope, too, as further explained in How can I open multiple files using "with open" in Python? .

with open('a', 'w') as a, open('b', 'w') as b:
    pass # do something with a and b here

If you want to do IPC, then use a TCP stream or a Pipe() (or better yet: Queue() ) instead.

Answer 2

You have to close the file after writing to make sure that everything is saved. So for the writing part you should add the lines

saveposx.close()
saveposy.close()