# Donchian 通道

> 原文：[`www.backtrader.com/recipes/indicators/donchian/donchian/`](https://www.backtrader.com/recipes/indicators/donchian/donchian/)

```py
`class DonchianChannels(bt.Indicator):
  '''
 Params Note:
 - `lookback` (default: -1)
 If `-1`, the bars to consider will start 1 bar in the past and the
 current high/low may break through the channel.
 If `0`, the current prices will be considered for the Donchian
 Channel. This means that the price will **NEVER** break through the
 upper/lower channel bands.
 '''

    alias = ('DCH', 'DonchianChannel',)

    lines = ('dcm', 'dch', 'dcl',)  # dc middle, dc high, dc low
    params = dict(
        period=20,
        lookback=-1,  # consider current bar or not
    )

    plotinfo = dict(subplot=False)  # plot along with data
    plotlines = dict(
        dcm=dict(ls='--'),  # dashed line
        dch=dict(_samecolor=True),  # use same color as prev line (dcm)
        dcl=dict(_samecolor=True),  # use same color as prev line (dch)
    )

    def __init__(self):
        hi, lo = self.data.high, self.data.low
        if self.p.lookback:  # move backwards as needed
            hi, lo = hi(self.p.lookback), lo(self.p.lookback)

        self.l.dch = bt.ind.Highest(hi, period=self.p.period)
        self.l.dcl = bt.ind.Lowest(lo, period=self.p.period)
        self.l.dcm = (self.l.dch + self.l.dcl) / 2.0  # avg of the above` 
```
