Hi, If you want to play around with a copy of Sage built using Python3 instead of Python2 (so 'export SAGE_PYTHON3="yes"') without having to build or install anything, send me an email (wstein@gmail.com) and I'll add you to a CoCalc project that has Sage built that way. See how long until it breaks for you on your favorite Sage commands. For me, it broke pretty quickly: ``` sage: print(2,3) 2 3 sage: range(10) range(0, 10) sage: {'a', 'b'} {'a', 'b'} sage: M = ModularSymbols(23) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) in () ----> 1 M = ModularSymbols(Integer(23)) /home/user/sage/local/lib/python3.6/site-packages/sage/modular/modsym/modsym.py in ModularSymbols(group, weight, sign, base_ring, use_cache, custom_init) 346 key = canonical_parameters(group, weight, sign, base_ring) 347 --> 348 if use_cache and key in _cache: 349 M = _cache[key]() 350 if not (M is None): return M TypeError: unhashable type: 'Gamma0_class_with_category' ``` -- William Note by Samuel: [as Erik Bray pointed out on sage-devel](https://groups.google.com/d/msg/sage-devel/oar-UzFXM8g/J8jGSPnXAQAJ), things got better for modular symbols in Sage 8.4.rc0. Illustration: ``` sage: print(version()) # version of Sage SageMath version 8.4.rc0, Release Date: 2018-10-07 ``` ``` sage: print(sys.version) # version of Python 3.6.6 (default, Oct 8 2018, 20:46:03) [GCC 7.3.0] ``` ``` sage: print(2, 3) 2 3 sage: range(10) range(0, 10) sage: {'a', 'b'} {'a', 'b'} ``` ``` sage: M = ModularSymbols(23) sage: M Modular Symbols space of dimension 5 for Gamma_0(23) of weight 2 with sign 0 over Rational Field sage: M.basis() ((1,0), (1,17), (1,19), (1,20), (1,21)) ``` To learn more about modular symbols: - https://wstein.org/books/modform/modform/modular_symbols.html To participate in the effort to port Sage to Python 3, see: - [Sage Trac ticket 15530: Metaticket: Add support for python 3.6+](https://trac.sagemath.org/ticket/15530) - [Sage wiki page: Python3-compatible code](https://wiki.sagemath.org/Python3-compatible%20code)