[docs] Problem With Python Arithmetic

[John Hulbert]

Hello.

I don't know if this is a bug in Python, or my own misuse of the language.

I have the following code:

p=3470494144279007
p=(p*3+1)/2
print(p)

p=3470494144279007.0
p=(p*3+1)/2
print(p)

These should give the same answer, but I get the following 2 answers, 
with the first one correct, and the second one wrong. (They differ in 
the last integer digit):

5205741216418511.0
5205741216418510.0

Also, can you tell me (a Python beginner), how I can force Python to use 
long integer arithmetic throughout an algorithm?

Regards

John Hulbert,
(Reading, UK)