100 digit floating point python

Question

I have a large decimal number, such as the square root of 2, and I want to view the first 100 decimal digits. However, float does not support this capability: 1.4142135623730951454746218587388284504413604736328125000000000000000000000000000000000000000000000000

What is the best way to do this? I do not want to import anything, preferably

Answer 1

If your requirement for precision is 100 decimal digits, I think you have to use decimal.Decimal.

The float in Python is not designed for this kind of precise calculation.

Using decimal.Decimal is almost as simple as float, you can do +, -, *, / and some other commonly used calculations directly between any decimal.Decimal without any consideration.

Also, decimal.Decimal supports setting up the precision directly you want:

>>> from decimal import getcontext, Decimal
>>> getcontext().prec = 6
>>> Decimal(1) / Decimal(7)
Decimal('0.142857')
>>> getcontext().prec = 28
>>> Decimal(1) / Decimal(7)
Decimal('0.1428571428571428571428571429')

You can find more detail in this Python2 API or Python3 API