Considerations for using division in Python

The examples in this paper explain the considerations of the use of division in Python, which is a very important technique, and it is very useful for Python program design. The specific analysis is as follows:

Here's an example:

def avg (First, *rest):   return (first + sum (rest))/(1 + len (rest)) # Sample Use AVG (1, 2)    

The source program just to demonstrate the use of variable-length parameters, but in the Python 2.7.1 interpreter, I get the result is not the same as the result of the comment

>>> def avg (First, *rest): ...   return (first + sum (rest))/(1 + len (rest)) ...  

It can be clearly seen that the data after the decimal point is truncated, I remember dividing two integers, "//" should be the rounding, I remember wrong?

>>> def avg (First, *rest): ...   return (first + sum (rest))//(1 + len (rest)) # change "/' to '//' ...  

Change the "/" to "//", the result is the same, "//" is indeed to take the whole point I remember correctly, but why "/" The result is also truncated?

The same procedure I tested in 3.4.1 's interpreter and got the desired result:

>>> def avg (First, *rest): ...   return (first + sum (rest))/(1 + len (rest  )) ... >>> avg (1, 2) 1.5 >>> avg (1, 2, 3, 4) 2.5 >>> def avg (First, *rest): ...   return (first + sum (rest))//(1 + len (rest)) # change "/' to '//' ...  

You can see that in 3.4.1 's interpreter, the "/" result retains the decimal place, and "//" is the result of rounding.

After searching, I found the question on StackOverflow: How does the Force division in Python result in a floating-point number? Note that this is for the 2.x version, 3.x there is no such problem
The first two solutions to the answer are good:

Method 1:

Method 2:

Similar to the practice in the C language:

c = a/float (b)

I believe that the examples described in this article will be helpful to everyone's Python programming.

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