I found *asmeurer <https://github.com/asmeurer>* comment here:
http://stackoverflow.com/questions/27872250/plus-minus-operator-for-python
<http://stackoverflow.com/questions/27872250/plus-minus-operator-for-python-%C2%B1?newreg=30588109db764915ac50e0d3ef492569>
.
It`s very useful but I`m still stacked:
from sympy import *
pm = Symbol(u'±') # The u is not needed in Python 3. I used ± just for
pretty printing purposes. It has no special meaning.
k = 0
l = 0
m = 0
f1 = 1; f2 = 2; f3 = 3
# expr = k*f1 + pm*f2 + pm*f3
# expr1 = k*f1; expr2 = l*f2; expr3 = m*f3
# expr = expr1 + pm*expr2 + pm*expr3
expr1list = []
# expr2pos = expr2.subs(pm, 1)
# expr2neg = expr2.subs(pm, -1)
# expr2list = []
# expr2list.append(expr1.subs(pm, 1))
# expr2list.append(expr1.subs(pm, -1))
#
# expr3pos = expr3.subs(pm, 1)
# expr3neg = expr3.subs(pm, -1)
# expr3list = []
# expr3list.append(expr1.subs(pm, 1))
# expr3list.append(expr1.subs(pm, -1))
for k in range(0,3):
for l in range(0,3):
for m in range(0,3):
if k+l+m == 3:
expr1 = k*f1; expr2 = l*f2#; expr3 = m*f3
expr = expr1 + pm*expr2
expr1pos = expr.subs(pm, 1)
expr1neg = expr.subs(pm, -1)
expr1list.append(expr.subs(pm, 1))
expr1list.append(expr.subs(pm, -1))
for p1 in expr1list:
print (k,l,m)
print expr1list
print expr
print 'next triple'
gives a lot of errors. The last this one: UnicodeEncodeError: 'ascii' codec
can't encode character u'\xb1' in position 0: ordinal not in range(128).
But if I try *asmeurer <https://github.com/asmeurer>*`s example from the
link above it works fine.
Could anybody help for the newbe?
понедельник, 4 апреля 2016 г., 16:32:53 UTC+3 пользователь Dos18i2-se
Beaverov написал:
>
> Hi, I would like to calculate equations like this:
>
> z = part1 (+/-) part2 (+/-) part3 ... (+/-) partN.
>
> In case of 3 parts it`s rather easy to code all variants of equations (z1
> = part1 + part2 + part3; z2 = part1 + part2 - part3; z3 = part1 - part2 -
> part3; z4 = part1 - part2 + part3). But in case of four or higher numbers
> of equation parts it seems borring.
> Can I use sympy for this task? Could you please give some simple example
> or some key words for search in the google?
> Thanks in advance.
>
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