PyDOS shell simulation

I have a big project called 'PyDOS', written in Python 3.4, and it's going very well. Post your answers of anything that could make it look cleaner.

```
import time
import os
import sys
import random
import operator

def textviewer():
os.system('cls' if os.name == 'nt' else 'clear')
print ("Text Viewer.")
file_name = input("Enter a text file to view: ")
file = open(file_name, "r")
print ("Loading text...")
time.sleep(4)
os.system('cls' if os.name == 'nt' else 'clear')
print(file.read())
input("Press enter to close")
def edit():
os.system('cls' if os.name == 'nt' else 'clear')
print ("EDIT")
print ("-------------")
print ("Note: Naming this current document the same as a different document will replace the other document with this one.")
filename = input("Plese enter a file name.")
file = open(filename, "w")
print ("FILE: " +filename+".")
line1 = input()
line2 = input()
line3 = input()
line4 = input()
line5 = input()
file.write(line1)
file.write("\n")
file.write(line2)
file.write("\n")
file.write(line3)
file.write("\n")
file.write(line4)
file.write("\n")
file.write(line5)
file.close()
print ("File successfully saved as: " +filename+"!")
time.sleep(3)

while True:
os.system('cls' if os.name == 'nt' else 'clear')
print ()
print ("PyDOS VERSION 1.5")
shell = input("> ")
if shell == "textviewer":
print ("Loading Text Viewer...")
time.sleep(3)
textviewer()

elif shell == "edit":
print ("Loading edit...")
time.sleep(3)
edit()

elif shell == "dir":
print ("The drive name is A:")
print ()
print ("NAME: TYPE: MODIFIED:")
print ("SHUTDOWN.EXE .EXE 12/01/15 ")
print ("EDIT.EXE .EXE 12/01/15 ")
print ("TEXTVIEWER.EXE .EXE 12/01/15 ")

elif shell == "cls":
os.system('cls' if os.name == 'nt' else 'clear')

elif s

5 lines ought to be enough for everyone

The following has no meaning. Why 5?

line1 = input()
line2 = input()
line3 = input()
line4 = input()
line5 = input()

Instead let the user end:

def get_lines():
    print("Enter 'END' to end.")
    lines = []
    line = input()
    while line != 'END':
         lines.append(line)
         line = input()
    return lines

Now you can write:

lines = get_lines()
file.write('\n'.join(lines))

Programming with with

with is an extremely useful idiom because it handles closing files automagically.

with open(filename,'r') as f:
    f.read()
# The file is closed automatically :)

If considered harmful (if overused)

So you just started programming and think "Oh the if statements are so good they feel so CS" (I felt that way too when I started programming when I was 15 so I understand you).

BUT so many if and elif are repetitive and you should not repeat yourself.

I would suggest the high level dictionary to accomplish the task more shortly.

command_actions = {
    'textviewer' : textviewer,
    'edit' : edit,
    'dir' : print_dir,
    'cls' : clear_screen,
    'shutdown' : shutdown,
    'help' : give_help
    }
if shell in command_actions:
    action = command_actions[shell]
    action()
else:
    error_message()

Be helpful

It is common and good practice to show some help/info if the user types in help.

Who sleeps too much does not catch fish annoys the user

Why do you sleep up to 4 seconds?

time.sleep(4)

Ok, this emulates an ancient terminal but really, you don't want to make the user wait so much without reason. I suggest time.sleep(0.5)

StackExchange Code Review Q#83790, answer score: 17