python - How do I fix this speed varible writing back to file? -

i've been writing program, i've run error. current code is:

import tkinter tk speed = 80 def onkeypress(event, value):     global speed      text.delete("%s-1c" % 'insert', 'insert')     text.insert('end', 'current speed: %s\n\n' % (speed, ))     open("speed.txt", "r+") p:         speed = p.read()         speed = int(speed)     speed = min(max(speed+value, 0), 100)     open("speed.txt", "r+") p:         p.writelines(str(speed))     print(speed)     if speed == 100:         text.insert('end', 'you have reached speed limit')     if speed == 0:         text.insert('end', 'you can not go slower')    speed = 80  root = tk.tk() root.geometry('300x200') text = tk.text(root, background='black', foreground='white', font=('comic sans ms', 12)) text.pack()  # individual key bindings root.bind('<keypress-w>', lambda e: onkeypress(e, 1))  root.bind('<keypress-s>', lambda e: onkeypress(e, -1)) #  root.mainloop() 

i believe speed = min(...) causing error. guys have idea?

one problem (i guess it's problem you're having) trying overwrite content of file speed.txt, however, value writing contains fewer characters contained in file.

this can lead unexpected values winding in file, e.g. if file contains

 10 

consider happens if try decrement value 1 (user hit s key):

with open('speed.txt', 'r+') p:     speed = int(p.read())  speed -= 1    # speed 9  open("speed.txt", "r+") p:     p.writelines(str(speed)) 

speed.txt contains:

 90 

instead of decreasing speed 9, has been increased 90! if speed 100 , tried decrement it, end 990 in file.

this because opening file mode r+ opens file reading , writing , positions file pointer @ beginning of file. write overwrite first n characters n length of data written. hence can sort of corruption shown above.

you can fix opening file mode 'w' _second__ open(). overwrite file. , don't need use writelines(), use write().