Python Programming Python 3

How do you use a dictionary to assign "codes" to each letter of the alphabet?

My program 2 does not write out the text correctly when decoding because the codes have duplicate characters. It does not know which character is actually the letter and it puts both.

def main():

    codes = {'A':'6', 'a':'~', 'B':'66', 'b':';', 'C':'<', 'c':'@', 'D':'%$', 'd':'#', \
'E':'5', 'e':'$', 'F':'3', 'f':'%', 'G':'71', 'g':'^', 'H':'72', 'h':'&', 'I':'4', 'i':'*', \
         'J':'74', 'j':'(', 'K':'75', 'k':')', 'L':'1', 'l':'_', 'M':'77', 'm':'`', 'N':'/:', \
         'n':'-', 'O':'79', 'o':'+', 'P':'2', 'p':'=', 'Q':'99', 'q':'9', 'R':'82', 'r':'>', 'S':'83', \
         's':'[','T':'', 't':']', 'U': ';', 'u':'{', 'V':'86', 'v':'}', 'W':'7', 'w':'/', \
         'X':'/+', 'x':'8', 'Y':'%(', 'y':'0', 'Z':'90', 'z':'$122'}

    encr_file = open('newtext.txt','r')

    file_read = encr_file.read()

    encr_file.close()

    codes_items = codes.items()

    for ch in file_read:
        if not ch in codes.values() or ch == '.':
            print(ch,end='')
        else:
            for k,v in codes_items:
                if ch == v and ch != '.':
                    print(k,end='')

main()

File Encryption and Decryption
Write a program that uses a dictionary to assign A????1codesA????1 to each letter of the alphabet. For example:
codes = { 'A' : '%', 'a' : '9', 'B' : '@', 'b' : '#', etc . . .} Using this example, the letter A would be assigned the symbol %, the letter a would be assigned the number 9, the letter B would be assigned the symbol @, and so forth.

The program should open a specified text file, read its contents, and then use the dictionary to write an encrypted version of the fileA????1s contents to a second file. Each character in the second file should contain the code for the corresponding character in the first file.

Write a second program that opens an encrypted file and displays its decrypted contents on the screen