Hammer

A small body at the top of the range with a long lower shadow, appearing after a decline: sellers pushed price down and were rejected before the close. Returns +1.

Signature

Hammer(trend_period, body_ratio, shadow_ratio, on=<source>)

Argument	Type	Required	Notes
trend_period	int Param or literal	Yes	Bars back used to establish the prior trend. Default 5, bounds 1–100.
body_ratio	float Param or literal	Yes	Largest body, as a fraction of the range. Default 0.33, bounds 0.05–0.9.
shadow_ratio	float Param or literal	Yes	Minimum shadow length in body-multiples. Default 2.0, bounds 1.0–10.0.
on=	symbol	No	Source symbol. Defaults to the trade symbol. Reads open, high, low, close.

Formula

Small body near the high, lower shadow at least shadow_ratio × body, upper shadow no larger than the body, and the close below the close trend_period bars ago.

Warmup

trend_period bars, to establish the prior decline.

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

    def execute(self):
        p = Hammer(5, 0.33, 2.0, on=self.trade)
        sma = SMA(50, on=self.trade)
        if p.value > 0 and self.trade.is_flat:
            self.buy(self.trade, reason="Hammer after a decline")
        if self.trade.is_long and self.trade.close < sma.value:
            self.sell(self.trade, self.trade.position, reason="Trend lost")

Notes

• The prior-downtrend condition is what separates a hammer from a hanging man — identical geometry, opposite meaning. Here it is an explicit close-versus-close test over trend_period.