Template Variables

Does This Change Affect Me?

Read this section if you set Cylc template variables on the command line using the -s, --set or -set-file options.

This does not affect the Rose jinja2:suite.rc and empy:suite.rc variables set using the -S option to the rose suite-run command.


Template variables are passed to Jinja2 or EmPy for parsing the workflow definition in the flow.cylc file.

In Cylc 7 template variables could only be strings, in Cylc 8 they can be any valid Python literal including numbers, booleans, and lists.


Strings must be explicitly quoted i.e. key="value" rather than key=value.


Setting template variables on the command line:

# Cylc 7
cylc run <suite> -s 'FOO=abc'
# Cylc 8
cylc play <flow> -s 'FOO="abc"'

Setting template variables in a “set file” (using --set-file):

# Cylc 7
FOO = abc
BAR = bcd

# Cylc 8
FOO = "abc"
BAR = "bcd"

New Features

Any valid Python literals

Template variables can now be any valid Python literals e.g:

"string"   # string
123        # integer
12.34      # float
True       # boolean
None       # None type
[1, 2, 3]  # list
(1, 2, 3)  # tuple
{1, 2, 3}  # set
{"a": 1, "b": 2, "c": 3}  # dictionary

See Default Values and Template Variables for more information.

Shorthand for list of strings

New in version 8.2.

A new shorthand argument (-z/--set-list/--set-template) has been introduced allowing easier definition of template variables containing lists of strings on the command line:

# Before (still works)
cylc <command> --set "X=['a', 'b', 'c']"

# After
cylc <command> --set-list X=a,b,c