DragonflyDoji — Dragonfly Doji

A doji whose open and close sit at the top of the range, with a long lower shadow: sellers took price down through the session and were rejected entirely. Bullish; returns +1.

Signature

DragonflyDoji(lookback, body_ratio, shadow_ratio, on=<source>)

Argument	Type	Required	Notes
lookback	int Param	Yes	Pinned at 1. Bounds 1–1.
body_ratio	float Param or literal	Yes	Largest body as a fraction of the range. Default 0.05, bounds 0.001–0.5.
shadow_ratio	float Param or literal	Yes	Largest upper shadow as a fraction of the range. Default 0.1, bounds 0.0–0.5.
on=	symbol	No	Source symbol. Defaults to the trade symbol. Reads open, high, low, close.

Formula

Tiny body, upper shadow within shadow_ratio of the range; the rest of the range is the lower shadow.

Warmup

None.

Reading the value

p.value
p > 0

Pattern indicators return a flag, not a level: +1 bullish, -1 bearish, 0 absent. They are zero on most bars by design, so treat them as event triggers rather than as something to smooth or cross.

Example

class DragonflyEntry(Strategy):
    """Act on the pattern only in the direction of the longer trend."""
    trade = Symbol()
    sizing = FixedCapital()

    def execute(self):
        p = DragonflyDoji(1, 0.05, 0.1, on=self.trade)
        sma = SMA(50, on=self.trade)
        if p.value > 0 and self.trade.is_flat:
            self.buy(self.trade, reason="Dragonfly doji")
        if self.trade.is_long and self.trade.close < sma.value:
            self.sell(self.trade, self.trade.position, reason="Trend lost")

Notes

• Geometrically a doji-bodied hammer. Unlike Hammer it does not require a prior downtrend, so it fires more often and means less on its own.