stable/freqtrade/plugins/pairlist/pairlist_helpers.py

import re
from typing import List


def expand_pairlist(wildcardpl: List[str], available_pairs: List[str],
                    keep_invalid: bool = False) -> List[str]:
    """
    Expand pairlist potentially containing wildcards based on available markets.
    This will implicitly filter all pairs in the wildcard-list which are not in available_pairs.
    :param wildcardpl: List of Pairlists, which may contain regex
    :param available_pairs: List of all available pairs (`exchange.get_markets().keys()`)
    :param keep_invalid: If sets to True, drops invalid pairs silently while expanding regexes
    :return expanded pairlist, with Regexes from wildcardpl applied to match all available pairs.
    :raises: ValueError if a wildcard is invalid (like '*/BTC' - which should be `.*/BTC`)
    """
    result = []
    if keep_invalid:
        for pair_wc in wildcardpl:
            try:
                comp = re.compile(pair_wc)
                result_partial = [
                    pair for pair in available_pairs if re.fullmatch(comp, pair)
                ]
                # Add all matching pairs.
                # If there are no matching pairs (Pair not on exchange) keep it.
                result += result_partial or [pair_wc]
            except re.error as err:
                raise ValueError(f"Wildcard error in {pair_wc}, {err}")

        for element in result:
            if not re.fullmatch(r'^[A-Za-z0-9/-]+$', element):
                result.remove(element)
    else:
        for pair_wc in wildcardpl:
            try:
                comp = re.compile(pair_wc)
                result += [
                    pair for pair in available_pairs if re.fullmatch(comp, pair)
                ]
            except re.error as err:
                raise ValueError(f"Wildcard error in {pair_wc}, {err}")
    return result