How to round each item in a list of floats to 2 decimal places?

Question

I have a list which consists of float values but they\'re too detailed to proceed. I know we can shorten them by using the (\"%.f\" % variable) operator, like:

Answer 1

You might want to look at Python's decimal module, which can make using floating point numbers and doing arithmetic with them a lot more intuitive. Here's a trivial example of one way of using it to "clean up" your list values:

>>> from decimal import *
>>> mylist = [0.30000000000000004, 0.5, 0.20000000000000001]
>>> getcontext().prec = 2
>>> ["%.2f" % e for e in mylist]
['0.30', '0.50', '0.20']
>>> [Decimal("%.2f" % e) for e in mylist]
[Decimal('0.30'), Decimal('0.50'), Decimal('0.20')]
>>> data = [float(Decimal("%.2f" % e)) for e in mylist]
>>> data
[0.3, 0.5, 0.2]