Working with Files

Syntax

Attribuut	Mode	Description
“r”	Read	Default value. Opens a file for reading, error if the file does not exist
“a”	Append	Opens a file for appending, creates the file if it does not exist
“w”	Write	Opens a file for writing, creates the file if it does not exist
“x”	Create	Creates the specified file, returns an error if the file exists
“t”	Text	Default value. Text mode
“b”	Binary	Binary mode (e.g. images)

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile.txt")


if __name__ == "__main__":
    main()

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile.txt", "rt")


if __name__ == "__main__":
    main()

Reading files

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile.txt", "r")
    print(f.read())


if __name__ == "__main__":
    main()

Example:

#!/usr/bin/env python3

def main():
    f = open("../demofile.txt", "r")
    print(f.read())


if __name__ == "__main__":
    main()

Read only part of the file

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile.txt", "r")
    print(f.read(5))


if __name__ == "__main__":
    main()

Read lines

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile.txt", "r")
    print(f.readline())


if __name__ == "__main__":
    main()

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile.txt", "r")
    print(f.readline())
    print(f.readline())


if __name__ == "__main__":
    main()

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile.txt", "r")
    for x in f:
        print(x)


if __name__ == "__main__":
    main()

Closing

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile.txt", "r")
    print(f.readline())
    f.close()


if __name__ == "__main__":
    main()

Writing files

open and read the file after the appending:

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile2.txt", "a")
    f.write("Now the file has more content!")
    f.close()

    #open and read the file after the appending:
    f = open("demofile2.txt", "r")
    print(f.read())


if __name__ == "__main__":
    main()

open and read the file after the appending

Example:

#!/usr/bin/env python3

def main():
    f = open("demofile3.txt", "w")
    f.write("Woops! I have deleted the content!")
    f.close()

    f = open("demofile3.txt", "r")
    print(f.read())


if __name__ == "__main__":
    main()

Create a new file

“x”, “a”, “w”

Example:

#!/usr/bin/env python3

def main():
    f = open("myfile.txt", "x")


if __name__ == "__main__":
    main()

Example:

#!/usr/bin/env python3

def main():
    f = open("myfile.txt", "w")


if __name__ == "__main__":
    main()

Delete a file or folder

Example:

#!/usr/bin/env python3

import os

def main():
    os.remove("demofile.txt")


if __name__ == "__main__":
    main()

Example:

#!/usr/bin/env python3

import os

def main():
    if os.path.exists("demofile.txt"):
        os.remove("demofile.txt")
    else:
        print("The file does not exist")


if __name__ == "__main__":
    main()

Example:

#!/usr/bin/env python3

import os

def main():
    os.rmdir("demodir")


if __name__ == "__main__":
    main()