Step 1: Write the given equation.
The relation between \(x\) and \(y\) is
\[
x-y=\pi
\]
Here \(\pi\) is a constant.
Step 2: Differentiate both sides with respect to $x$.
\[
\frac{d}{dx}(x-y) = \frac{d}{dx}(\pi)
\]
Step 3: Compute derivatives.
\[
\frac{d}{dx}(x)=1
\]
\[
\frac{d}{dx}(y)=\frac{dy}{dx}
\]
Thus
\[
1-\frac{dy}{dx}=0
\]
Step 4: Solve for $\dfrac{dy{dx}$.
\[
\frac{dy}{dx}=1
\]
Step 5: Conclusion.
Hence the rate of change of \(y\) with respect to \(x\) is \(1\).
Final Answer: $\boxed{1}$