So I am VERY new to programming and I started with Python 3. I started reading "Learn Python the Hard Way". Now, I got to a point where I had this code:

```
x = "There are %d types of people." % 10
binary = "binary"
do_not = "don't"
y = "Those who know %s and those who %s" % (binary, do_not)

print(x)
print(y)
print("I said: %r") % x

```

I do not really know the difference between `%r`, `%s` and `%d`. The error I get is `TypeError: unsupported operand type(s) for %: 'NoneType' and 'str'` No idea what to do and how to fix it. Please explain how I can actually make it work and why it won't work. Also, what is the difference between %r,d and s? Any useful links? Thank you in advance.