UDF in xlwings calculating with defined precision using Python Decimal or mpmath

Question

I am trying to use UDF in xlwings and I want to achieve required precision as both libraries Python Decimal and mpmath allows for this. I am calculating 2 ^ 0.5 with following functions:

@xw.func
def fce_2(x, y):
    import decimal
    from decimal import Decimal
    decimal.getcontext().prec = 100
    z = Decimal(x)** Decimal(y)
      
    return z

This returns 1,4142

AND

@xw.func
def fce_1(x, y):
    from mpmath import mp
    mp.dps = 100
    z = mp.mpf(x)** mp.mpf(y)
      
    return z

Returns 1,414213562 None of them returns the required number of decimal places which should be 100.

Answer 1

Numbers in Excel cells are always stored as 64 bit double floats, having about 15 significant digits. It should be possible to display more digits as string, use return str(z).