You can use this node to evaluate a string as a Jinja2 template. Note, however, that because ComfyUI's frontend uses {} for syntax, There are the following modifications to Jinja syntax:

{% %} becomes <% %>
{{ }} becomes <= =>
{# #} becomes <# #>

Functions in Jinja templates

The following functions and constants are available:

pi
min, max, clamp(minimum, value, maximum),
abs, round, ceil, floor
sqrt sin, cos, tan, asin, acos, atan. These functions are rounded to two decimals

In addition, a special steps function exists.

The steps function will generate a list of steps for iterating.

You can call it either as steps(end), steps(end, step=0.1) or steps(start, end, step). step is an optional parameter that defaults to 0.1. It'll return steps inclusive of start and end as long as step doesn't go past the end.

The second form is equivalent to steps(step, end, step). i.e. it starts at the first step.