如何获取 sympy 表达式中的符号列表? [英] How can I get a list of the symbols in a sympy expression?
问题描述
例如,如果我运行
import sympyx, y, z = sympy.symbols('x:z')f = sympy.exp(x + y) - sympy.sqrt(z)
是否有任何 f
方法可以用来获取表达式包含的 sympy.Symbol
对象的列表或元组?我宁愿不必解析 srepr(f)
或通过 f.args
向下解析.
在这种情况下,g.args[0].args[1].args[0]
给了我 Symbol("z")
,而 g.args[1].args[0].args
给了我元组 (Symbol("x"), Symbol("y"))
,但显然这些是表达式-具体.
您可以使用:
f.free_symbols
这将返回一组所有免费符号.
示例:
<预><代码>>>>进口同情>>>x, y, z = sympy.symbols('x:z')>>>f = sympy.exp(x + y) - sympy.sqrt(z)>>>f.free_symbols设置([x,z,y])For example, if I run
import sympy
x, y, z = sympy.symbols('x:z')
f = sympy.exp(x + y) - sympy.sqrt(z)
is there any method of f
that I can use to get a list or tuple of sympy.Symbol
objects that the expression contains? I'd rather not have to parse srepr(f)
or parse downward through f.args
.
In this case, g.args[0].args[1].args[0]
gives me Symbol("z")
, while g.args[1].args[0].args
gives me the tuple (Symbol("x"), Symbol("y"))
, but obviously these are expression-specific.
You can use:
f.free_symbols
which will return a set of all free symbols.
Example:
>>> import sympy
>>> x, y, z = sympy.symbols('x:z')
>>> f = sympy.exp(x + y) - sympy.sqrt(z)
>>> f.free_symbols
set([x, z, y])
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