Python 3.3.5 float format precision [duplicate]

Question

>>> '{:0.10}'.format(1/3)
'0.3333333333'
>>> '{:0.10}'.format(100/3)
'33.33333333'

The first gives 10 digits after the decimal point, the second gives 8. Does "precision" mean total digits? How do I control significant digits after the decimal point only?

Answer 1

You need to include the type f (for float) to control the number of digits after the decimal place:

>>> '{:.10f}'.format(100/3)
'33.3333333333'

Without specifying the type, Python falls back to the general number type and the number is rounded to the specified number of significant digits. From the documentation:

The precision is a decimal number indicating how many digits should be displayed after the decimal point for a floating point value formatted with 'f' and 'F', or before and after the decimal point for a floating point value formatted with 'g' or 'G'.