Simple Python Script question...

[Eremis]

Hi everybody!

I just started learning python (have a background in java), and I am using a "Learning Python O'REILLY" book. However I tried making a simple script that would convert text to binary, one letter at a time with a for loop...

Here's an example of my logic:

read a file to a string --> convert string to a list (ex. "Hello" --> ['H','e','l','l','o']) --> convert each letter to a int (ex. ord('H')) --> convert each int into bin (ex. bin(num)) --> put all the binary numbers into array --> print them to a diffrent file...

The result:

File1.txt --> Hello
File2.txt --> 0b1001000 0b1100101 0b1101100 0b1101100 0b1101111

Here's my code so far:


#!usr/bin/python26

#
# Description:
# Text to binary converter
# converts using regular ascii code
#
# Developer:
# Eremis
#

import sys

if len(sys.argv) != 2:
print "\n\t Text to Binary Converter 1.0 "
print "\t ---------------------------------------------------\n"
print "\t Usage: ./TextToBin.py <inputFile.txt>\n"
sys.exit(1)

# reading input file...
try:
text = open(sys.argv[1], "r").readlines()
except(IOError):
print "[-] Error: Check your text file path\n"
sys.exit(1)

listText = list(text)
listOutText = []

for c in listText:
listOutText[c] = bin(ord(listText[c]))

print listOutText


Every time I run this I get an error: Why?, and How can I fix it?



Traceback (most recent call last):
File "TextToBin.py", line 31, in <module>
listOutText[c] = bin(ord(listText[c]))
TypeError: list indices must be integers, not str


Thanks for the help1

[kostkon]

You can change it to

listText = list(text)
listOutText = []

for c in listText:
listOutText.append(bin(ord(c)))
or to

listText = list(text)
listOutText = []

for c in range(len(listText)):
listOutText[c] = bin(ord(listText[c]))



for c in listText just iterates throught the char of listText and thus c is a char and not an int index.

[Eremis]

Oh, ok!

Thank you so much!

[Eremis]

I thought I solved it, but I still keep getting error...

Traceback (most recent call last):
File "TextToBin.py", line 31, in <module>
listOutText[c] = bin(ord(listText[c]))
TypeError: ord() expected a character, but string of length 7 found

[kostkon]

although as I can see it now, the second code part

for c in range(len(listText)):
listOutText[c] = bin(ord(listText[c]))
will most likely throw an error.

Eh, thus, it should be:

for c in range(len(listText)):
listOutText.append(bin(ord(listText[c])))
or even more compactly if you want

listOutText = [bin(ord(listText[c])) for c in range(len(listText))]
or

listOutText = [bin(ord(c)) for c in listText]

[kostkon]

I thought I solved it, but I still keep getting error...

Traceback (most recent call last):
File "TextToBin.py", line 31, in <module>
listOutText[c] = bin(ord(listText[c]))
TypeError: ord() expected a character, but string of length 7 found
Oh ok, you are reading every line of the file and save it to a list, thus every list item contains a line of text.

thus, you could change to something like this:

for line in text:
binline = ""
for char in line:
binline += (bin(ord(char)))
listOutText.append(binline)

This will give you a new list containing the same lines but with the text converted to binary.

[Eremis]

Ok, this last one worked, Thanks!

(I just need to get better in python for loops, still thinking in java...)
I think I understand it now... I was trying to convert the whole line... right?

Well thanks again...

Python should be thought in schools insted of java...

[kostkon]

I was trying to convert the whole line... right
In:

for c in listText:
listOutText[c] = bin(ord(listText[c]))
you were trying to use c as an index but actually the code

for c in listText
iterates through the list and assigns the value of each of its item to c which in this case every item is a line of text.
Secondly, yeah, you were trying to convert the whole line to binary, wheres the ord() method accepts only one character and that most likely would have thrown a TypeError exception if the loop was working right.

Thus, you have to iterate through the text list and get each line and then iterate through each line to get the individual characters.
As you can see, you can iterate through a string as you would iterate through a list, by simply using a for loop.

and this line

listText = list(text)
is not needed, since it just copies the text list to a new list.

Hope the above makes some sense. :(