Checking var is a number?

[Fredrik Lundh]

dav.phillips at ntlworld.com wrote:

> I am very new to all this and need to know how to check
> a variable to see if it is a number or not.

assuming that "variable" means "string object" and "number" means 
"integer", you can use the isdigit predicate:

     if var.isdigit():
         print "all characters in", var, "are digits"

if you want to check for anything that can be converted to a float, the 
best way is to do the conversion and trap any ValueError that may occur:

     try:
	value = float(var)
     except ValueError:
         print "not a valid float"

if you want an integer instead, replace "float" with "int".

if you had something else in mind, let us know.

 > Also can anyone recommend a reference book apart from dive into python
 > preferably a reference with good examples of how to impliment code.

you can find an extensive list of available books here:

     http://wiki.python.org/moin/PythonBooks

some on-line code collections:

     http://aspn.activestate.com/ASPN/Python/Cookbook/
     http://effbot.org/zone/librarybook-index.htm

and don't forget the core references:

     http://docs.python.org/lib/
     http://docs.python.org/ref/

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