如何在Python 2.7中正确使用字符串格式？

Question

Ok, please bear with me, I'm completely new to this. This is for school, and the exact syntax isn't important here for my assignment, but for my own personal knowledge I want to know a little more about string formatting.

whenever I use %f it defaults to 2 decimal places. Is there a string format that I can use on a float that will show the float with the number of decimals it actually has?

for instance my list contains 2.0, 2.01, 2.001, 2.0001 and I want to use a string format to print them as they look. Which format code would I use or how could I use %f properly if possible?

This is in Python 2.7 on Windows 7(if that matters).

Answer 1

If you convert the float to a string, then when you print it, it will be displayed just as you wrote it.

>>> x = str(2.0)
>>> print(x)
2.0
>>> x = str(2.01)
>>> print(x)
2.01
>>> x = str(2.001)
>>> print(x)
2.001
>>> x = str(2.0001)
>>> print(x)
2.0001

(In fact, to be precise, in Python you're not actually converting the floating point object, but creating a string object that looks like it. But that's a bit outside of the scope of your question.)

UPDATE

Someone posted a way to remove trailing zeros from floating point numbers using the Decimal class, here: Removing Trailing Zeros in Python

Answer 2

%g may be what you're looking for:

>>> "%g, %g, %g, %g" % (2.1, 2.01, 2.001, 2.0001)
'2.1, 2.01, 2.001, 2.0001'