On 25 February 2013 00:08, <piterrr.dolin...@gmail.com> wrote: Chris Angelico wrote: >> For example (I believe it's already been mentioned) "declaring" intX with >> some integer value does *nothing* to maintain >> >> X as an integer: >> >> --> intX = 32 >> >> --> intX = intX / 3.0 >> >> --> intX >> >> 10.6666666666 >> > > Yes I did see that it is possible to redefine the type of a variable. But I > don't think I would ever do this intentionally; need to be really careful > with Python.
You do need to be careful around types in Python (as in all languages). It took some time for me to understand how to use types in Python. After a while I came to realise that not knowing exactly the type of a particular object is not as much of a problem as I initially thought. Once you understand how to use this ambiguity to your advantage it becomes possible to write very flexible code that can be reused without ambiguity in situations that you haven't yet anticipated. The key mental hurdle, I think, is to realise that instead of relying on compilation errors to spot (a small subset of) your programming errors, you are relying on runtime exceptions. Python still gives errors when you use an object in a way that is inconsistent with its type; you just don't see those errors at compile time. The trickier cases are ones where two types are very similar and can be used similarly in most, but not all, situations. An example of this would be the one that Chris has highlighted where an object that you expected to be an int is actually a float. I find that I need to be careful when using division on quantities that I expected to be integers (true in all languages) and careful about the notation used in a numeric literal. Once you get used to it, you will find it easy to see that the '.0' that Chris appended was deliberate in order to control the type of the resulting object. Oscar -- http://mail.python.org/mailman/listinfo/python-list
