limit within a python function

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Defining a variable inside the function, we can use it for the limit.

For example, define t and substitute it for the variable provided by the user.

Applying this idea, we can define myfunction as follows:

def mylimit(f, x, a):
    r"""
    Return the limit of the expression `f` when `x` tends to `a`.
    """
    t = SR.var('t')
    return f.subs({x: t}).limit(t=a)

With that definition:

sage: mylimit(1/y, y, 2)
1/2