Le lundi 27 avril 2015 08:59:38 UTC+2, Loïc Gouarin a écrit :
>
>
>
> Le dimanche 26 avril 2015 21:03:02 UTC+2, Aaron Meurer a écrit :
>>
>> On Sun, Apr 26, 2015 at 12:27 AM, Loïc Gouarin <[email protected]>
>> wrote:
>> > Hi,
>> >
>> > I would like to parse a string expression like that
>> >
>> > from sympy.parsing.sympy_parser import parse_expr
>> > parse_expr("m[0][0]")
>> >
>> > But I have an error with 'Symbol' object does not support indexing.
>> >
>> > If I do
>> >
>> > sympy.Symbol("m[0][0]")
>> >
>> > everything is ok.
>> >
>> > I try to write my own transformation funtion that takes the "m[x][y]"
>> and
>> > creates a Symbol and add it to the standard_transformations in
>> parse_expr
>> > but the problem is still the same because the problem is in auto_symbol
>> and
>> > it parses again my string 'm[x][y]'.
>>
>> Does it work if you transform it literally to sympy.Symbol("m[0][0]")?
>>
>> Hi Aaron,
>
> your solution is almost what I want. There is no error in the parse_exp
> but I have in the result Symbol("m[x][y]") and not m[x][y]. I know thatit
> is the same but I parse again the result and I need m[x][y].
>
> Is there an easy way to have on the ouput m[x][y] and not
> Symbol("m[x][y]") ?
>
>
Ok I found my error. My transformation was incorrect. I wrote
from sympy.parsing.sympy_parser import parse_expr, standard_transformations
def auto_moments(tokens, local_dict, global_dict):
result = []
i = 0
while(i < len(tokens)):
tokNum, tokVal = tokens[i]
if tokVal == 'm':
name = ''.join([val for n, val in tokens[i:i+7]])
result.append((tokNum, 'Symbol("{0}")'.format(name)))
i += 7
else:
result.append(tokens[i])
i += 1
return result
s = parse_expr("m[0][0]", transformations=(auto_moments,) +
standard_transformations)
The result was
Symbol("m[0][0]")
But if I write
from sympy.parsing.sympy_parser import parse_expr, standard_transformations
def auto_moments(tokens, local_dict, global_dict):
result = []
i = 0
while(i < len(tokens)):
tokNum, tokVal = tokens[i]
if tokVal == 'm':
name = ''.join([val for n, val in tokens[i:i+7]])
result.extend([(1, 'Symbol'), (51, '('), (3, "'{0}'".format(name
)), (51, ')')])
i += 7
else:
result.append(tokens[i])
i += 1
return result
s = parse_expr("m[0][0]", transformations=(auto_moments,) +
standard_transformations)
print s
Now it is ok. I have
m[0][0]
Thanks,
Loic
Thanks,
> Loic
>
> Aaron Meurer
>>
>> >
>> > Could you tell me how I can do that ?
>> >
>> > Thanks,
>> > Loic
>> >
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