Question

Python

Add a command to this chapter’s case study program that allows the user to view the contents of a file in the current working directory. When the command is selected, the program should display a list of filenames and a prompt for the name of the file to be viewed.

Be sure to include error recovery in the program. If the user enters a filename that does not exist they should be prompted to enter a filename that does exist.

An example of the program input and output is shown below:

/root/sandbox
1   List the current directory
2   Move up
3   Move down
4   Number of files in the directory
5   Size of the directory in bytes
6   Search for a file name
7   View the contents of a file
8   Quit the program
Enter a number: 7

Files in /root/sandbox:
filesys.py
example.txt
Enter a file name from these names: example.txt

THIS IS CONTENT OF AN EXAMPLE FILE.

/root/sandbox
1   List the current directory
2   Move up
3   Move down
4   Number of files in the directory
5   Size of the directory in bytes
6   Search for a file name
7   View the contents of a file
8   Quit the program
Enter a number: 8

Have a nice day!

Code to use:

"""

File: filesys.py

Project 6.6

Provides a menu-driven tool for navigating a file system

and gathering information on files.

Adds a command to view a file's contents.

"""

import os, os.path

QUIT = '8'

COMMANDS = ('1', '2', '3', '4', '5', '6', '8')

MENU = """1   List the current directory

2   Move up

3   Move down

4   Number of files in the directory

5   Size of the directory in bytes

6   Search for a file name

8   Quit the program"""

def main():

    while True:

        print(os.getcwd())

        print(MENU)

        command = acceptCommand()

        runCommand(command)

        if command == QUIT:

            print("Have a nice day!")

            break

def acceptCommand():

    """Inputs and returns a legitimate command number."""

    while True:

        command = input("Enter a number: ")

        if not command in COMMANDS:

            print("Error: command not recognized")

        else:

            return command

def runCommand(command):

    """Selects and runs a command."""

    if command == '1':

        listCurrentDir(os.getcwd())

    elif command == '2':

        moveUp()

    elif command == '3':

        moveDown(os.getcwd())

    elif command == '4':

        print("The total number of files is", \

              countFiles(os.getcwd()))

    elif command == '5':

        print("The total number of bytes is", \

              countBytes(os.getcwd()))

    elif command == '6':

        target = input("Enter the search string: ")

        fileList = findFiles(target, os.getcwd())

        if not fileList:

            print("String not found")

        else:

            for f in fileList:

                print(f)

     # add your condition here

def viewFile(dirName):

   # write your code here

   print("")

def listCurrentDir(dirName):

    """Prints a list of the cwd's contents."""

    lyst = os.listdir(dirName)

    for element in lyst: print(element)

def moveUp():

    """Moves up to the parent directory."""

    os.chdir("..")

def moveDown(currentDir):

    """Moves down to the named subdirectory if it exists."""

    newDir = input("Enter the directory name: ")

    if os.path.exists(currentDir + os.sep + newDir) and \

       os.path.isdir(newDir):

        os.chdir(newDir)

    else:

        print("ERROR: no such name")

def countFiles(path):

    """Returns the number of files in the cwd and

    all its subdirectories."""

    count = 0

    lyst = os.listdir(path)

    for element in lyst:

        if os.path.isfile(element):

            count += 1

        else:

            os.chdir(element)

            count += countFiles(os.getcwd())

            os.chdir("..")

    return count

def countBytes(path):

    """Returns the number of bytes in the cwd and

    all its subdirectories."""

    count = 0

    lyst = os.listdir(path)

    for element in lyst:

        if os.path.isfile(element):

            count += os.path.getsize(element)

        else:

            os.chdir(element)

            count += countBytes(os.getcwd())

            os.chdir("..")

    return count

def findFiles(target, path):

    """Returns a list of the file names that contain

    the target string in the cwd and all its subdirectories."""

    files = []

    lyst = os.listdir(path)

    for element in lyst:

        if os.path.isfile(element):

            if target in element:

                files.append(path + os.sep + element)

        else:

            os.chdir(element)

            files.extend(findFiles(target, os.getcwd()))

            os.chdir("..")

    return files

if __name__ == "__main__":

    main()

Answer 1