Question

Just for fun, I wrote this simple function to reverse a string in Python:

def reverseString(s):
    ret = ""
    for c in s:
        ret = c + ret
    return ret

Now, if I pass in the following two strings, I get interesting results.

print reverseString("Pla\net")
print reverseString("Plan\et")

The output of this is

te
alP
te\nalP

My question is: Why does the special character \n get translated into a new line when passed into the function, but not when the function parses it together by reversing n\? Also, how could I stop the function from parsing \n and instead return n\?

Answer 1

You should take a look at the individual character sequences to see what happens:

>>> list("Pla\net")
['P', 'l', 'a', '\n', 'e', 't']
>>> list("Plan\et")
['P', 'l', 'a', 'n', '\\', 'e', 't']

So as you can see, \n is a single character while \e are two characters as it is not a valid escape sequence.

To prevent this from happening, escape the backslash itself, or use raw strings:

>>> list("Pla\\net")
['P', 'l', 'a', '\\', 'n', 'e', 't']
>>> list(r"Pla\net")
['P', 'l', 'a', '\\', 'n', 'e', 't']