Conditionals

%reload_ext rubberize
from rubberize.config import config

By default, Rubberize renders only the lines within the True path of the conditional ladder, with the condition itself being displayed as an introductory expression.

The lines within the True path are indented to visually indicate that they belong to this block. The other branches are not rendered.

%%tap
x = 5
if x > 0:
    y = x**2

\( \displaystyle x = 5 \)

\( \displaystyle \text{Since}\ x > 0\ \to\ 5 > 0 \text{:} \)

\( \displaystyle y = x^{2} = 5^{2} = 25 \)

If no conditions are True, nothing in the conditional block will be rendered.

%%tap
x = -5
if x > 0:
    y = x**2

\( \displaystyle x = -5 \)

However, if an else statement is provided, lines in else will be rendered without any indentation and introductory expression.

%%tap
x = -5
if x > 0:
    y = x**2
else:
    y = -x**2
y + 10

\( \displaystyle x = -5 \)

\( \displaystyle y = -x^{2} = -\left( -5 \right)^{2} = -25 \)

\( \displaystyle y + 10 = -25 + 10 = -15 \)

Warning

Gotcha: Rubberize generates the rendering based on the actual execution of the Python code.

If a test within the conditional ladder alters the value being tested, Rubberize will use the altered value in generating the rendered output. This means that if the value is modified within the conditional block, the render may not appear as expected.

This code will not render properly:

%%tap
x = 5
if x > 0:
    x = -1

\( \displaystyle x = 5 = -1 \)

because for Rubberize, the value of x is -1, not 5.

To avoid confusion and ensure accurate rendering, do not modify the value being tested within the conditional ladder. Keep the value consistent across the conditions to avoid unexpected behavior in the rendered output.

Skipping Code with pass

When Rubberize encounters a conditional ladder where the True path contains only a pass statement, nothing will be rendered.

%%tap
x = 5
if x > 0:
    pass
x + 3

\( \displaystyle x = 5 \)

\( \displaystyle x + 3 = 5 + 3 = 8 \)

A common usage pattern is when certain calculation lines are needed only when specific conditions are met, and the presentation should remain silent otherwise.

In this pattern, the if branch contains the negation of the condition and uses pass to suppress output. The else branch then contains the calculation that should be rendered when the condition is actually true.

For example:

%%tap
temp_c = -3

if not (temp_c < 0):
    pass
else:
    temp_c * 1.8 + 32

\( \displaystyle \mathrm{temp}_{c} = -3 \)

\( \displaystyle \mathrm{temp}_{c} \cdot 1.80 + 32 = -3 \times 1.80 + 32 = 26.60 \)

Here the conversion to Fahrenheit is rendered only when the temperature is below zero. If the temperature is zero or positive, the pass branch runs and Rubberize produces no output for the conditional.

This pattern allows the code to control when a calculation appears while keeping the conditional logic hidden in the rendered presentation.

As Piecewise Assignment

If all of the branches in the conditional ladder only contain a single assignment statement to the same variable, it will be rendered as a piecewise assignment to the target variable when @show_substitution=False (or @nosub, @def).

THe inline comment on the first assignment will be used as annotation.

Note

Options and shortcuts applied to the if keyword line applies to the whole if-elif-else ladder.

%%tap
x = 3
if x > 0:  # @show_substitution=False
    y = x + 1  # Value of y
else:
    y = x - 1

\( \displaystyle x = 3 \)

\( \displaystyle y = \begin{cases} \displaystyle x + 1, &\text{if}\ x > 0 \\ \displaystyle x - 1, &\text{otherwise} \end{cases} = 4 \)

Value of y

Showing All Conditions

To show all the conditions in a conditional ladder, turn off both the substitution and result display modes by setting @show_substitution=False @show_result=False, or using @def.

%%tap
x = 3
if x > 0:  # @def
    y = x + 1
    z = x - 1
else:
    y = x - 1
    z = x + 1

\( \displaystyle x = 3 \)

\( \displaystyle \text{If}\ x > 0 \text{:} \)

\( \displaystyle y = x + 1 \)

\( \displaystyle z = x - 1 \)

\( \displaystyle \text{Otherwise:} \)

\( \displaystyle y = x - 1 \)

\( \displaystyle z = x + 1 \)

If @show_substitution=False @show_result=True and the conditional block cannot be rendered as a piecewise assignment, An error will be raised, prompting you to set @show_result=False.

Rendering Summary

Shortcut	Definition	Substitution	Result	Branch shown
@all	True	True	True	True path only.
@nodef	False	True	True	True path only.
@nosub	True	False	True	As piecewise if possible, otherwise RubberizeNotImplementedError
@nores	True	True	False	True path only.
@def	True	False	False	As piecewise if possible, otherwise all branches.
@sub	False	True	False	True path only.
@res	False	False	True	Single result if possible, otherwise RubberizeNotImplementedError
@none	False	False	False	Single target if possible, otherwise all branches.