Python : Console Question

I was writing this code for the Pyg Latin Convertor and something occured to me.

As you can see in the first image,when I entered some string without a space in the console, the program accepted the input.But as you can see in the second image when entered the same string with a space in between it prints the else section of the code.Does this happen due to the use of .isalpha() method? And if yes then why so?
Thank You!!

spaces are not alphanumeric characters.

If i where you, i would enter the space here:

raw_input("Enter a word: ")

so the user doesn’t have to.

Thank you for the help!