TEX commands as input in SymPy

[redsto...@163.com]

Is there any function in SymPy can take this TEX command as an input

(-6x^2-x-7)(2x^3+3x^2-2x-5)

to find the derivative?

[Jason Moore]

We don't have a full LaTeX parser in SymPy. If this is the only expression you are interested in, simply:

import sympy

x = sympy.symbols('x')

expr = (-6 * x**2 - x - 7) * (2 * x**3 + 3 * x**2 - 2 * x - 5)

expr.diff(x)

Jason
moorepants.info
+01 530-601-9791

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[Mateusz Paprocki]

Hi,

I wanted to suggest a mathematica parser for this:

In [1]: import sympy.parsing.mathematica as m

In [2]: m.parse("(-6x^2-x-7)(2x^3+3x^2-2x-5)")
Out[2]: '(-6*x**2-x-7)*(2*x**3+3*x**2-2*x-5)'

In [3]: eval(_)
Out[3]:
⎛ 2 ⎞ ⎛ 3 2 ⎞
⎝- 6⋅x - x - 7⎠⋅⎝2⋅x + 3⋅x - 2⋅x - 5⎠

But there is bug there and the above output requires the following patch:

diff --git a/sympy/parsing/mathematica.py b/sympy/parsing/mathematica.py
index f86d59a..eeb12f7 100644
--- a/sympy/parsing/mathematica.py
+++ b/sympy/parsing/mathematica.py
@@ -39,7 +39,7 @@ def parse(s):
(r"\A\((.+)\)([\w\.].*)\Z", # Implied multiplication - (a)b
lambda m: "(" + parse(m.group(1)) + ")*" + parse(m.group(2))),

- (r"\A([\d\.]+)([a-zA-Z].*)\Z", # Implied multiplicatin - 2a
+ (r"\A([+-]?[\d\.]+)([a-zA-Z].*)\Z", # Implied multiplicatin - 2a
lambda m: parse(m.group(1)) + "*" + parse(m.group(2))),

(r"\A([^=]+)([\^\-\*/\+=]=?)(.+)\Z", # Infix operator

Mateusz

[Aaron Meurer]

Have a look at parse_expr() in sympy.parsing.sympy_parser.

Aaron Meurer

> To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAGBZUCZfJVXw27Rh0U31ST9tU%3DwZbkuqUS792ff364JYvdG%2BHg%40mail.gmail.com.

[redsto...@163.com]

>>> from sympy.parsing.sympy_parser import parse_expr

>>> parse_expr("(-6x^2-x-7)(2x^3+3x^2-2x-5)")

Traceback (most recent call last):

  File "<pyshell#25>", line 1, in <module>

    parse_expr("(-6x^2-x-7)(2x^3+3x^2-2x-5)")

  File "C:\Python34\lib\site-packages\sympy\parsing\sympy_parser.py", line 757, in parse_expr

    return eval_expr(code, local_dict, global_dict)

  File "C:\Python34\lib\site-packages\sympy\parsing\sympy_parser.py", line 691, in eval_expr

    code, global_dict, local_dict)  # take local objects in preference

  File "<string>", line 1

    (-Integer (6 )Symbol ('x' )^Integer (2 )-Symbol ('x' )-Integer (7 ))(Integer (2 )Symbol ('x' )^Integer (3 )+Integer (3 )Symbol ('x' )^Integer (2 )-Integer (2 )Symbol ('x' )-Integer (5 ))

                       ^

SyntaxError: invalid syntax

>>> 

在 2014年10月9日星期四UTC+8上午3时37分07秒，Aaron Meurer写道：

[redsto...@163.com]

>>> from sympy.parsing.sympy_parser import parse_expr

>>> parse_expr("(-6x^2-x-7)(2x^3+3x^2-2x-5)")

Traceback (most recent call last):

  File "<pyshell#25>", line 1, in <module>

    parse_expr("(-6x^2-x-7)(2x^3+3x^2-2x-5)")

  File "C:\Python34\lib\site-packages\sympy\parsing\sympy_parser.py", line 757, in parse_expr

    return eval_expr(code, local_dict, global_dict)

  File "C:\Python34\lib\site-packages\sympy\parsing\sympy_parser.py", line 691, in eval_expr

    code, global_dict, local_dict)  # take local objects in preference

  File "<string>", line 1

    (-Integer (6 )Symbol ('x' )^Integer (2 )-Symbol ('x' )-Integer (7 ))(Integer (2 )Symbol ('x' )^Integer (3 )+Integer (3 )Symbol ('x' )^Integer (2 )-Integer (2 )Symbol ('x' )-Integer (5 ))

                       ^

SyntaxError: invalid syntax

>>> 

在 2014年10月9日星期四UTC+8上午3时37分07秒，Aaron Meurer写道：

Have a look at parse_expr() in sympy.parsing.sympy_parser.

[redsto...@163.com]

can you send me the patch file ,I am not familiar with git .

在 2014年10月8日星期三UTC+8下午9时42分16秒，Mateusz Paprocki写道：

[redsto...@163.com]

I can get the string representation of (-6x**2-x-7)*(2*x**3+3*x**2-2*x-5),is there anyway we can use this string directly to  find the derivative?

>>> from sympy.parsing.mathematica import *

>>> parse('(-6x^2-x-7)(2x^3+3x^2-2x-5)')

'(-6x**2-x-7)*(2*x**3+3*x**2-2*x-5)'

在 2014年10月8日星期三UTC+8下午8时17分47秒，Jason Moore写道：

[Aaron Meurer]

You have to enable various transformers like implicit multiplication.
See help(parse_expr)

Aaron Meurer

> https://groups.google.com/d/msgid/sympy/2ca9f2ab-6070-4fe9-b896-131d5b36c53f%40googlegroups.com.

[Chris Smith]

The parser was fixed as indicated at http://stackoverflow.com/questions/26249993/6x2-x-72x33x2-2x-5-as-input-in-sympy

>>> from sympy.parsing.mathematica import mathematica as m

>>> m('(-6 * x**2 - x - 7) * (2 * x**3 + 3 * x**2 - 2 * x - 5)')

(-6*x**2 - x - 7)*(2*x**3 + 3*x**2 - 2*x - 5)

>>> _.diff(x)

(-12*x - 1)*(2*x**3 + 3*x**2 - 2*x - 5) + (-6*x**2 - x - 7)*(6*x**2 + 6*x - 2)

[redstone-cold]

Is there any way to simplify (-12*x - 1)*(2*x3 + 3*x2 - 2*x - 5) + (-6*x2 - x - 7)*(6*x2 + 6*x - 2) ？ I want to get the final result ,not an intermediate one.

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[Aaron Meurer]

Use simplify()

Aaron Meurer

> https://groups.google.com/d/msgid/sympy/5f2010a.1ee40.149420210e4.Coremail.redstone-cold%40163.com.