# Sympy integration algorithm towards -infinity

 1 Following achrzesz hint about integral's algorithm option, I tried (Sage 4.7.2): integral(1/x^2, x, -infinity, -1, algorithm='sympy')  Unfortunately, I got: Traceback (click to the left of this block for traceback) ... AttributeError: 'MinusInfinity' object has no attribute '_sympy_'  What's going wrong? asked Jan 21 '12 Green diod 63 ● 5 ● 12 The workarounds are good for now. I've opened the auspicious ticket # 12345 (http://trac.sagemath.org/sage_trac/ticket/12345) for the underlying issue.kcrisman (Jan 23 '12)

 1 It seems to be a bug. sympy can recognize infinity but not minus infinity of sage. You can try to directly call sympy integrate instead import sympy as sp a=sp.Symbol('a') b=sp.integrate(1/x^2,(x,a,-1))._sage_() b.substitute(a=-oo)  posted Jan 21 '12 Shashank 1570 ● 5 ● 22 ● 55 How do you get this infinity symbol? But most importantly, do you input this code in a simple python interpreter or in Sage? What is this _sage_() method?Green diod (Jan 23 '12)How do you get this infinity symbol?Green diod (Jan 23 '12)Every element from another program (such as sympy) has a _sage_ method to convert its things back to Sage objects. The infinity symbol is just one of the several ways to represent infinity in Sage (and several other programs of this type); in principle, it should be equivalent to using infinity, but apparently this bug leaves it to not work for Sympy.kcrisman (Jan 23 '12)All right, but how do you input the infinity symbol?Green diod (Jan 23 '12)1-oo is just minus oo the alphabetsShashank (Jan 23 '12) see 1 more comment
 1 sage: from sympy import * sage: integrate(1/x^2, (x, -oo, -1), algorithm='sympy') 1 posted Jan 21 '12 achrzesz 1661 ● 4 ● 16 ● 36 How do you get this infinity symbol?? Anyway, I still get the same error even at the console using -infinityGreen diod (Jan 23 '12)

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