String formatting in Python: can I use %s for all types?

Question

When doing string formatting in Python, I noticed that %s transforms also numbers to strings.

>>> a = 1
>>> b = 1.1
>>> c = 'hello'
>>> print 'Integer: %s; Float: %s; String: %s' % (a, b, c)
Integer: 1; Float: 1.1; String: hello

I don't know for other variable types, but is it safe to use %s like this?

It is certainly quicker than specifying always the type each time.

Answer 1

using %s automatically calls str on the variable. Since everything has __str__ defined, you should be able to do this without a problem (i.e. no exception will be raised). However, what you actually will have printed is another story ...

Note that in newer python code, there's another option which uses the format method:

'Integer: {}; Float: {}; String: {}'.format(a,b,c)

This works basically the same way except that it is more powerful once you learn the syntax.