Print Brian2 unit error messages

print_unit_errors.py

from brian2 import *

# A little script to get an overview over the new error messages for unit
# errors in Brian 2 (in the form of a table that can be pasted into github)

if __name__ == '__main__':

    @check_units(x=volt, y=1, result=amp)
    def myfunc(x, y):
        if y == 0:
            return 1*mA
        else:
            return 1*ms

    from __builtin__ import sum as python_sum

    expressions = ['3*mV+5*mA',
                   'sin(5*mV)',
                   'np.where(True, (np.arange(10)*mV), (np.arange(10)*mA))',
                   '3*mV -1',
                   '1 - 3*mV',
                   '2 ** (3*mV)',
                   'Quantity(2, force_quantity=True) ** (3*mV)',
                   '3 % (3*mV)',
                   '3*mV % 5*mA',
                   'max(1*mV, 2*mV, 3*mA)',
                   'max([1*mV, 2*mV, 3*mA])',
                   '3*mV < 5*mA',
                   '3*mV >= 5*mA',
                   '3 >= 5*mA',
                   '3*mV >= 5',
                   '5*second == 3*volt',
                   '5*second != 3*volt',
                   'python_sum([3*mV, 4*mV, 5*mA])',
                   'hypot(3*um, 4*um)',
                   'hypot(3*um, 4)',
                   'hypot(3, 4*um)',
                   'myfunc(3*mA, 0)',
                   'myfunc(3*mV, 1*ms)',
                   'myfunc(3*mA, 1*ms)',
                   'myfunc(3*mV, 1)',
                   ]

    G = NeuronGroup(10, '''x : 1
                           y : volt''', threshold='True')
    # If G.x would only have zeros, it could be used in the "0 has any units" way
    G.x = np.arange(10)

    statements = ['G.x = 3*mV',
                  'G.x = np.arange(10)*mV',
                  'G.y = 2*mA',
                  'G.y = 2',
                  'G.y = np.arange(10)*mA',
                  'G.y = np.arange(10)',
                  'G.y += G.x',
                  'G.y = G.x + G.y',
                  'G.x += G.y',
                  'G.x = G.x + G.y',
                  'x = np.arange(3)*mV; x += 1',
                  'x = np.arange(3)*mV; x += 1*mA',
                  'S = Synapses(G, G, "", pre="x+=1", delay=5*amp)',
                  'G2 = NeuronGroup(3, "dv/dt = -v/(10*ms) : 1 (unless refractory)", refractory=5*amp)']

    print 'Expression/Statement | Error message'
    print '-------------------- | -------------'

    for expr in expressions:
        try:
            result = eval(expr)
        except DimensionMismatchError as ex:
            print '`%s` | `%s`' % (expr, ex)

    for statement in statements:
        try:
            exec(statement)
        except DimensionMismatchError as ex:
            print '`%s` | `%s`' % (statement, ex)