[FIXED] Format number within a path name

Issue

I have a rule using files named with a series of numbers from 01, 02, 03 ... until 12 in their file name, and I would need to format them in 1, 2, 3... 12 for the next step in the analysis.

I am sure there is a way to do this with either f-strings or .format(), but I am not sure how to do it within one rule where I also specify the number series with a list.

How do I get there?

A minimal example (not working):

numbers = ["01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12"]

starting_folder = "project/temp"

rule rename_files:
    input: f"{starting_folder}/file.{{numbers}}.ext"
    output: f"{starting_folder}/file.{{{numbers}}:01d}_new.ext"
    shell: "ln -s {input} {output}"

E.g. I would like to get project/temp/file.1_new.ext as the output file path.

Solution

The way I would approach this problem is by using an input function, and formatting the expected output beforehand

numbers = ["01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12"]

# a dict mapping expected numbers to their old version, assuming they are unique 
expected_numbers = {n.lstrip("0") : n for n in numbers} 

def expected_file(wildcards):
    """Takes the expected output number and returns the input number"""
    old_number = expected_numbers[wildcards.number]
    return f"project/temp/file.{old_number}.ext"

rule rename_files:
    input: expected_file  # using the input function to get the expected file
    output: "project/temp/file.{number}_new.ext"
    shell: "ln -s {input} {output}"

rule target: 
    input: expand("project/temp/file.{number}_new.ext", number=expected_numbers)

This is a bit more verbose than SultanOrazbayev's answer, but maybe a tad more explicit ? It also allows to avoid escaping brackets in inputs and outputs or rules, which can be tricky to debug in bigger projects.

It is also using two snakemake features that can be useful to others :

• The expand function : https://snakemake.readthedocs.io/en/stable/snakefiles/rules.html#the-expand-function
• The use of an input function : https://snakemake.readthedocs.io/en/stable/snakefiles/rules.html#the-expand-function

Answered By - Lurk