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File line encryption

I am trying to write a program that opens a text file and shifts each of the characters in the file 5 characters to the right. He should do this only for alphanumeric characters and leave nonalphanumerics as they are. (for example: C becomes H) I have to use an ASCII table for this, and I have a problem when characters are wrapped. ex: w should become b, but my program gives me the character that is in the ASCII table. Another problem I am facing is that all characters are printed on separate lines, and I would like all of them to be printed on the same line. I can not use lists or dictionaries.

This is what I have, I'm not sure how to make the final if statement

def main(): fileName= input('Please enter the file name: ') encryptFile(fileName) def encryptFile(fileName): f= open(fileName, 'r') line=1 while line: line=f.readline() for char in line: if char.isalnum(): a=ord(char) b= a + 5 #if number wraps around, how to correct it if print(chr(c)) else: print(chr(b)) else: print(char)
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Using str.translate :

 In [24]: import string In [25]: string.uppercase Out[25]: 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' In [26]: string.uppercase[5:]+string.uppercase[:5] Out[26]: 'FGHIJKLMNOPQRSTUVWXYZABCDE' In [27]: table = string.maketrans(string.uppercase, string.uppercase[5:]+string.uppercase[:5]) In [28]: 'CAR'.translate(table) Out[28]: 'HFW' In [29]: 'HELLO'.translate(table) Out[29]: 'MJQQT'
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First, it matters if it has lower or upper case. I'm going to assume here that all characters are lowercase (if they weren’t, it would be easy enough to make them)

 if b>122: b=122-b #z=122 c=b+96 #a=97

w = 119 in ASCII and z = 122 (decimal in ASCII), so 119 + 5 = 124 and 124-122 = 2, which is our new b, then we add this to a-1 (this takes care if we get 1 back, 2 + 96 = 98 and 98 - b.

To print on the same line instead of printing when you have it, I would write them to a list and then create a line from that list.

but instead

  print(chr(c)) else: print(chr(b))

I would do

  someList.append(chr(c)) else: somList.append(chr(b))

then combine each item in the list together on one line.

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You can create a dictionary to process it:

 import string s = string.lowercase + string.uppercase + string.digits + string.lowercase[:5] encryptionKey = {s[i]:s[i+5] for i in range(len(s)-5)}

The final addition to s ( + string.lowercase[:5] ) adds the first 5 letters to the key. Then we use a simple understanding of the word to create an encryption key.

Put in your code (I also changed it so that you f.readline() over the lines and not use f.readline() :

 import string def main(): fileName= input('Please enter the file name: ') encryptFile(fileName) def encryptFile(fileName): s = string.lowercase + string.uppercase + string.digits + string.lowercase[:5] encryptionKey = {s[i]:s[i+5] for i in range(len(s)-5)} f= open(fileName, 'r') line=1 for line in f: for char in line: if char.isalnum(): print(encryptionKey[char]) else: print(char)
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