This function evaluates a given numerical expression upto a given floating point precision upto 100 digits. The function also takes subs parameter a dictionary object of numerical values for symbols. Consider following expression
>>> from sympy.abc import r >>> expr=pi*r**2 >>> expr
The above code snippet gives an output equivalent to the below expression −
Πr2Πr2
To evaluate above expression using evalf() function by substituting r with 5
>>> expr.evalf(subs={r:5})
The above code snippet gives the following output −
78.5398163397448
By default, floating point precision is upto 15 digits which can be overridden by any number upto 100. Following expression is evaluated upto 20 digits of precision.
>>> expr=a/b
>>> expr.evalf(20, subs={a:100, b:3})
The above code snippet gives the following output −
33.333333333333333333