str.format rounding to the left of the decimal

[ClassicalSoul]

Hi, I was wondering how I could make string.format round to the left of the decimal.

>>> x = 4. 542412343
>>> '{0} rounded to {1} decimals is {2: .1f}'.format(x, 4, x) 
>>> 4.5

>>> x = 52137809
>>> '{0} rounded to {1} decimals is {2: ???}'.format(x, 4, x) 
>>> 50000000

Moreover, is there somewhere I could have accessed this information, like the help function?

Thanks