format-py

#!/usr/bin/env bash
set -euo pipefail

valid_shebang='#!/usr/bin/env python'
updated=0

while IFS= read -r -d '' path; do
    first_line=''
    if IFS= read -r first_line < "$path"; then
        :
    fi
    if [[ "$first_line" == "$valid_shebang" ]]; then
        continue
    fi
    tmp="$(mktemp)"
    if [[ "$first_line" == '#!'* ]]; then
        {
            printf '%s\n' "$valid_shebang"
            tail -n +2 "$path"
        } > "$tmp"
    else
        {
            printf '%s\n' "$valid_shebang"
            cat "$path"
        } > "$tmp"
    fi
    chmod --reference="$path" "$tmp"
    mv "$tmp" "$path"
    printf 'updated %s\n' "$path"
    updated=$((updated + 1))
done < <(find solvers -maxdepth 1 -type f -name '*.py' -print0 | sort -z)

printf 'normalized %d solver Python files\n' "$updated"