How to implement Percentile indicator?

[rami]

pandas implementation

pctrank = lambda x: pd.Series(x).rank(pct=True).iloc[-1]
df["n200"]=df["source"].rolling(200).apply(pctrank)

backtrader implementation ?

class Percentile(bt.Indicator):
    lines = ('percentile',)
    params = (('period', 15),)

    def __init__(self):
        self.lines.percentilee = pd.Series(self.data).rank(pct=True).iloc[-1]

[backtrader]

It would seem you are looking for the PercentRank indicator.

Docs - Indicator Reference