CODEWITHSUNDEEP
pythonwhile-loop
01110100
01110100

Reputation: 833

What is incorrect with my infinite while loop?

Here is my code:

#!/usr/bin/env python

encodec = {
    'a':22 , 'b':24 , 'c':26 , 'd':28 , 'e':12 , 'f':14 , 'g': 16 , 'h':18 , 'i':32 , 'j':34 , 'k':36 , 'l':38 , 'm':42 , 'n':44 , 'o':46 , 'p':48 , 'q':50 , 'r':52 , 's':54 , 't':56 , 'u':58 , 'v': 62 , 'w':64 , 'x':66, 'y': 68 , 'z':72 , ' ':74 , '.':76 , ',':78 , "'":82 , '?':84 , '"':86
}
decodec = {
    22:'a' , 24:'b' , 26:'c' , 28:'d' , 12:'e' , 14:'f' , 16:'g' , 18:'h' , 32:'i' , 34:'j' , 36:'k' , 38:'l' , 42:'m' , 44:'n' , 46:'o' , 48:'p' , 50:'q' , 52:'r' , 54:'s' , 56:'t' , 58:'u' , 62:'v' , 64:'w' , 66:'x', 68:'y' , 72:'z' , 74:' ' , 76:"." , 78:',' , 82:"'" , 84:'?' , 86:'"'
}
option = raw_input("Would you like to 'encode' or 'decode' a word? ")
while option.lower() not in ('encode' , 'decode'):
    option = raw_input("Please enter a valid response ('encode' or 'decode'): ")

if option.lower() == 'encode':
    word = raw_input("Enter a string to be encoded: ").lower()
    length = len(word)
    z = 1
    result = []
    while z < length+1:
        a = word[z-1]
        result += str(encodec[a])
        z = z + 1
    print int(''.join(result))


elif option.lower() == 'decode':
    num = (raw_input("Enter your text to be decoded: "))
    length = len(num)
    z = 1
    result = []
    while z < length+1:
        a = num[z-1:z+1]
        result += str(decodec[int(a)])
        z = z + 1
    print ''.join(result)

This is the snippet that won't quite work:

elif option.lower() == 'decode':
    num = (raw_input("Enter your text to be decoded: "))
    length = len(num)
    z = 1
    result = []
    while z < length+1:
        a = num[z-1:z+1]
        result += str(decodec[int(a)])
        z = z + 1
    print ''.join(result)

I don't understand why this loop continues to loop. The conditional of the loop is that while the value of variable z is less than the value of the length, to continue the loop. The length doesn't increase in the loop, and I add a line in the loop that adds 1 to z every iteration. For some reason, though, it continues to loop infinitely. I dont understand why?

Upvotes: 0

Views: 155

Answers (2)

DSM
DSM

Reputation: 352979

Looks like inconsistent use of whitespace to me. Try running your code using

python -tt your_program_name.py

to confirm this. If I look at the raw code you've posted, the first snippet looks like this:

 "    elif option.lower() == 'decode':\n",
 '    \tnum = (raw_input("Enter your text to be decoded: "))\n',
 '    \tlength = len(num)\n',
 '    \tz = 1\n',
 '    \tresult = []\n',
 '    \twhile z < length+1:\n',
 '    \t\ta = num[z-1:z+1]\n',
 '    \t\tresult += str(decodec[int(a)])\n',
 '        \tz = z + 1\n',
 "        print ''.join(result)\n",
 '    \t\n',

and you can see the strange indentation of the z = z + 1 line. In particular, though it seems like you're using tabs for indentation, that line only has one tab, so even though it looks like it's correctly indented on the screen I don't think it's actually being executed because it's not actually inside the while loop.

Always use four-space tabs: makes life so much easier. Most editors can be configured to do this.

Upvotes: 6

jackcogdill
jackcogdill

Reputation: 5122

Does this code work for you?

elif option.lower() == 'decode':
    num = (raw_input("Enter your text to be decoded: "))
    result = ''
    index = 0
    while index < len(num) -1:
        result += decodec[int(num[index:index +2])]
        index += 2
    print result

If I set the input as 222426, the output is abc

Upvotes: 1

Related Questions