How do you assign a symbol in python?
In order to calculate derivatives and other expressions I used the sympy package and said that Show
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that looks like this:
with python I would like to change T (and rho) as a symbol to a value. How could I do that? So, I would like to create 10 numbers like Thanks for your help To begin, we should make something about SymPy clear. SymPy is nothing more than a Python library, like Symbols#One consequence of this fact is that SymPy can be used in any environment where Python is available. We just import it, like we would any other library: This imports all the functions and classes from SymPy into our interactive Python session. Now, suppose we start to do a computation. >>> x + 1 Traceback (most recent call last): ... NameError: name 'x' is not defined Oops! What happened here? We tried to
use the variable >>> x = symbols('x') >>> x + 1 x + 1
>>> x, y, z = symbols('x y z') As a final note, we note that the name of a Symbol and the name of the variable it is assigned to need not have anything to do with one another. >>> a, b = symbols('b a') >>> a b >>> b a Here we have done the very confusing thing of assigning a Symbol with the name >>> crazy = symbols('unrelated') >>> crazy + 1 unrelated + 1 This also shows that Symbols can have names longer than one character if we want. Usually, the best practice is to assign Symbols to Python variables of the same name, although there are exceptions: Symbol names can contain characters that are not allowed in Python variable names, or may just want to avoid typing long names by assigning Symbols with long names to single letter Python variables. To avoid confusion, throughout this tutorial, Symbol names and Python variable names will always coincide. Furthermore, the word “Symbol” will refer to a SymPy Symbol and the word “variable” will refer to a Python variable. Finally, let us be sure we understand the difference between SymPy Symbols and Python variables. Consider the following: x = symbols('x') expr = x + 1 x = 2 print(expr) What do you think the output of this code will be? If you thought >>> x = symbols('x') >>> expr = x + 1 >>> x = 2 >>> print(expr) x + 1 Changing >>> x = 'abc' >>> expr = x + 'def' >>> expr 'abcdef' >>> x = 'ABC' >>> expr 'abcdef' In this example, if we want to know what >>> x = symbols('x') >>> expr = x + 1 >>> expr.subs(x, 2) 3 Equals signs#Another very important consequence of the fact that SymPy does not extend Python syntax is that You may think, however, that Instead of treating >>> Eq(x + 1, 4) Eq(x + 1, 4) There is one additional caveat about >>> (x + 1)**2 == x**2 + 2*x + 1 False We got Recall from above that It turns out that when using SymPy as a library, having >>> a = (x + 1)**2 >>> b = x**2 + 2*x + 1 >>> simplify(a - b) 0 >>> c = x**2 - 2*x + 1 >>> simplify(a - c) 4*x There is also a method called >>> a = cos(x)**2 - sin(x)**2 >>> b = cos(2*x) >>> a.equals(b) True Two Final Notes: ^ and /#You may have noticed
that we have been using >>> True ^ False True >>> True ^ True False >>> Xor(x, y) x ^ y Finally, a small technical discussion on how SymPy works is in order. When you type something like This sort of operator magic happens automatically behind the scenes, and you rarely need to even know that it is happening. However, there is one exception. Whenever you combine a SymPy object and a SymPy object, or a SymPy object and a Python object, you get a SymPy object, but whenever you combine two Python objects, SymPy never comes into play, and so you get a Python object. >>> type(Integer(1) + 1) This is usually not a big deal. Python ints work much the same as SymPy Integers, but there is one important exception: division. In SymPy, the division of two Integers gives a Rational: >>> Integer(1)/Integer(3) 1/3 >>> type(Integer(1)/Integer(3)) But in Python >>> from __future__ import division >>> 1/2 0.5 To avoid this, we can construct the rational object explicitly This problem also comes up whenever we have a larger symbolic expression with This happens because Python first evaluates >>> x + Rational(1, 2) x + 1/2 There are several tips on avoiding this situation in the Gotchas and Pitfalls document. Further Reading#For more discussion on the topics covered in this section, see Gotchas and Pitfalls. How do you assign symbols in Python?1) Assign: This operator is used to assign the value of the right side of the expression to the left side operand.
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Assignment Operators in Python.. How do you assign a value to a symbol in Python?The assignment operator, denoted by the “=” symbol, is the operator that is used to assign values to variables in Python. The line x=1 takes the known value, 1, and assigns that value to the variable with name “x”. After executing this line, this number will be stored into this variable.
Can you use symbols in Python variables?Usually, the best practice is to assign Symbols to Python variables of the same name, although there are exceptions: Symbol names can contain characters that are not allowed in Python variable names, or may just want to avoid typing long names by assigning Symbols with long names to single letter Python variables.
What are the symbols in Python?Index – Symbols. ! ( exclamation) in a command interpreter. in curses module. ... . ! ( pdb command). ! patterns.. != operator, [1]. " (double quote) string literal.. """ string literal.. # (hash) comment, [1], [2] in doctests. in printf-style formatting, [1] ... . $ (dollar) environment variables expansion. in regular expressions.. |