r Open the file for reading.
r+ Open the file for reading and writing.
w Open the file for writing, overwriting existing files, and creating the file if it does not exist.
w+ Open the file for reading and writing, overwriting existing files, and creating the file if it does not exist.
a Open the file for writing, creating the file if it does not exist, and appending to the file if it does.
a+ Open the file for reading and writing, creating the file if it does not exist, and appending to the file if it does.
b Open the file in binary reading/writing mode (applicable only on Windows systems; however, recommended in all scripts).