wend.templates¶

Readymade templates: counter filename patterns.

Part 3 of Future Paths observes that sized and unsized counters are the same few t-strings written again and again. counter writes them once::

counter("log", width=5, suffix=".parquet")
# PathExpr('log_{idx:05d}.parquet')
counter("chunk", width=3, of_total=True, suffix=".parquet")
# PathExpr('chunk_{idx:03d}-of-{total:03d}.parquet')

A counter is an ordinary one-segment expression: join it below a directory, render it, match it, glob it. Its parameters are integers formatted with d, so matching parses them back as int, and a literal after each field that does not start with a digit keeps matching on its single-parse fast path.

counter ¶

counter(
    stem: str = "",
    *,
    width: int | None = None,
    suffix: str = "",
    of_total: bool = False,
    sep: str = "_",
    of: str = "-of-",
    idx: str | Param = "idx",
    total: str | Param = "total",
) -> PathExpr

A counter filename: {stem}{sep}{idx}{suffix}, or, with of_total, {stem}{sep}{idx}{of}{total}{suffix} (a sized counter, which says how many there are).

width zero-pads every number to that many digits ({idx:04d}); without it they are unpadded ({idx:d}). sep is only written when there is a stem. idx and total name the parameters, or are Params to use (declared type=int by default), so a declared default carries over: counter("chunk", of_total=True, total=Param("total", type=int, default=10)).