import re


def infer_delimiter(filename, comment_char="#", n_lines=3):
    """
    Given a file which contains data separated by one of the following:
        - commas
        - tabs
        - spaces
    Return the most likely separator by sniffing the first few lines
    of the file's contents.
    """
    lines = []
    with open(filename, "r") as f:
        for line in f:
            if line.startswith(comment_char):
                continue
            if len(lines) < n_lines:
                lines.append(line)
            else:
                break
    if len(lines) < n_lines:
        raise ValueError(
            "Not enough lines in %s to infer delimiter" % filename)
    candidate_delimiters = ["\t", ",", "\s+"]
    for candidate_delimiter in candidate_delimiters:
        counts = [len(re.split(candidate_delimiter, line)) for line in lines]
        first_line_count = counts[0]
        if all(c == first_line_count for c in counts) and first_line_count > 1:
            return candidate_delimiter
    raise ValueError("Could not determine delimiter for %s" % filename)