step is a pure-Python module providing a very simple template engine with minimum syntax. It supports variable expansion, flow control and embedding of Python code.
You can generate different strings from a template by providing a specific namespace.
Variables are enclosed in ${} and follow the same syntax rules as Python variables; e.g.:
This is variable x: ${x}
This is the third item of my_list: ${my_list[2]}
This is not a variable: $\{x\}
Flow control expressions are written like regular Python control structures, preceded by the % sign and must be closed by a %end<statement> tag; e.g.:
%if (x > 2):
x is greater than 2
%else:
x is ${x}
%endif
All text between <% and %> is considered Python code; you can use the builtin echo() function to output some text from within Python code blocks; e.g.:
<%
import time
echo("Current timestamp is {}".format(time.time()))
%>
<\% This is not Python code %\>
You can use the special function isdef() to perform some actions only if a name is defined in the template namespace; e.g.:
%if isdef("my_var")
my_var is ${my_var}
%endif
The setopt() function allows you to enable options that modify the template output; the only supported option is "strip", which removes leading/trailing whitespace, contiguous whitespace and empty lines and defaults to true; e.g.:
<%setopt("strip", True)%>
A backslash at the end of a line will suppress the newline character.
A simple example generating an HTML document:
import step
template = r"""
<%setopt("strip", False)%>
<html>
<head>
<title>${title}</title>
</head>
<body>
<h1>My Items</h1>
<ul>
%for item in items:
<li>${item}</li>
%endfor
</ul>
%if isdef("info"):
<p>${info}</p>
%endif
<footer>
<%
import time
echo("Last refresh: {}\n".format(time.ctime()))
%>
</footer>
</body>
</html>
"""
namespace = {"title": "My title",
"items": ["item 1", "item 2", "item 3"],
"info": "More interesting information"}
print step.Template(template).expand(namespace)