use std::process::Command; fn main() { let out = Command::new("python") .args(&["-c", "import sys; print(sys.version_info[1])"]) .output() .expect("python version did not print"); let version = u8::from_str_radix(String::from_utf8_lossy(&out.stdout).trim(), 10) .expect("python version was not parsed"); for each in 6..version { println!("cargo:rustc-cfg=python3{}", each); } }