how can i show an irrational number to 100 decimal places in python?
decimal module comes in handy.
>>> from decimal import *
>>> getcontext().prec = 100
>>> Decimal(2).sqrt()
Decimal('1.414213562373095048801688724209698078569671875376948073176679737990732478462107038850387534327641573')
You can use the decimal module for arbitrary precision numbers:
import decimal
d2 = decimal.Decimal(2)
# Add a context with an arbitrary precision of 100
dot100 = decimal.Context(prec=100)
print d2.sqrt(dot100)
If you need the same kind of ability coupled to speed, there are some other options: [gmpy], 2, cdecimal.