Snakemake one wildcard and also expand

Question

Is it possible to have a snakemake with a wildcard and expand:

rule a:
    input:
        "input/{first}.txt",
        expand("data/{second}.txt", second=A_LIST)
    output:
        expand("output/{first}_{second}, second=A_LIST)

Answer 1

Use double braces for wildcards, if your pattern has both wildcard and variable. For example, expand("output/{{first}}_{second}", second=A_LIST)

A_LIST = ['1', '2']

rule all:
    input:
        expand("output/abc_{second}", second=A_LIST)

rule a:
    input:
        "input/{first}.txt",
        expand("data/{second}.txt", second=A_LIST)
    output:
        expand("output/{{first}}_{second}", second=A_LIST)
    shell:
        "touch {output}"