round down to 2 decimal in python

Question

I need to round down and it should be two decimal places.
Tried the following,

a = 28.266
print round(a, 2)

28.27

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Answer 1

There's an even simpler way of doing this generically, by subtracting a small quantity before rounding, like so:

a = 28.269
digits = 2
print(round(a - 0.5/10**digits, digits))

This is based on the intuition that one way of rounding a float to the nearest integer is by adding 0.5, then truncating. The above solution does the opposite by subtracting a half of the minimal 'tick' that the desired precision allows, then rounding.