tradingview's pine script convert python

Question

Now convert to python from tradingview pine script. But have some problem. under function.

reso(exp, use, res) => use ? security(tickerid, res, exp) : exp

I don't understand to pine script security function. and don't convert to python.

original url: https://www.tradingview.com/script/X227SKSM-Open-Close-Cross-Strategy-R6-1-revised-by-yourmattie/

pine script source code:

//@version=2
strategy(title = "Open Close Cross Strategy", shorttitle = "OCC Strategy", overlay = true, pyramiding = 0, default_qty_type = strategy.percent_of_equity, default_qty_value = 10)
// === INPUTS ===
useRes = input(defval = true, title = "Use Alternate Resolution? ( 
recommended )")
stratRes = input(defval = "120", title = "Set Resolution ( should not be lower than chart )", type = resolution)
useMA = input(defval = true, title = "Use MA? ( otherwise use simple Open/Close data )")
basisType = input(defval = "DEMA", title = "MA Type: SMA, EMA, DEMA, TEMA, WMA, VWMA, SMMA, HullMA, LSMA, ALMA ( case sensitive )", type = string)
basisLen = input(defval = 14, title = "MA Period", minval = 1)
offsetSigma = input(defval = 6, title = "Offset for LSMA / Sigma for ALMA", minval = 0)
offsetALMA = input(defval = 0.85, title = "Offset for ALMA", minval = 0, step = 0.01)
useStop = input(defval = true, title = "Use Trailing Stop?")
slPoints = input(defval = 200, title = "Stop Loss Trail Points", minval = 1)
slOffset = input(defval = 400, title = "Stop Loss Trail Offset", minval = 1)
// === /INPUTS ===
// === BASE FUNCTIONS ===
// Returns MA input selection variant, default to SMA if blank or typo.
variant(type, src, len, offSig, offALMA) =>
 v1 = sma(src, len) // Simple
 v2 = ema(src, len) // Exponential
 v3 = 2 * v2 - ema(v2, len) // Double Exponential
 v4 = 3 * (v2 - ema(v2, len)) + ema(ema(v2, len), len) // Triple Exponential
 v5 = wma(src, len) // Weighted
 v6 = vwma(src, len) // Volume Weighted
 v7 = na(v5[1]) ? sma(src, len) : (v5[1] * (len - 1) + src) / len // Smoothed
 v8 = wma(2 * wma(src, len / 2) - wma(src, len), round(sqrt(len))) // Hull
 v9 = linreg(src, len, offSig) // Least Squares
 v10 = alma(src, len, offALMA, offSig) // Arnaud Legoux
 type=="EMA"?v2 : type=="DEMA"?v3 : type=="TEMA"?v4 : type=="WMA"?v5 : type=="VWMA"?v6 : type=="SMMA"?v7 : type=="HullMA"?v8 : type=="LSMA"?v9 : type=="ALMA"?v10 : v1
// security wrapper for repeat calls
reso(exp, use, res) => use ? security(tickerid, res, exp) : exp
// === /BASE FUNCTIONS ===
// === SERIES SETUP ===
// open/close
closeSeries = useMA ? reso(variant(basisType, close, basisLen, offsetSigma, offsetALMA), useRes, stratRes) : reso(close, useRes, stratRes)
openSeries = useMA ? reso(variant(basisType, open, basisLen, offsetSigma, offsetALMA), useRes, stratRes) : reso(open, useRes, stratRes)
trendState = closeSeries > openSeries ? true : closeSeries < openSeries ? false : trendState[1]
// === /SERIES ===
// === PLOTTING ===
barcolor(color = closeSeries > openSeries ? #006600 : #990000, title = "Bar Colours")
// channel outline
closePlot = plot(closeSeries, title = "Close Line", color = #009900, linewidth = 2, style = line, transp = 90)
openPlot = plot(openSeries, title = "Open Line", color = #CC0000, linewidth = 2, style = line, transp = 90)
// channel fill
closePlotU = plot(trendState ? closeSeries : na, transp = 100, editable = false)
openPlotU = plot(trendState ? openSeries : na, transp = 100, editable = false)
closePlotD = plot(trendState ? na : closeSeries, transp = 100, editable = false)
openPlotD = plot(trendState ? na : openSeries, transp = 100, editable = false)
fill(openPlotU, closePlotU, title = "Up Trend Fill", color = #009900, transp = 40)
fill(openPlotD, closePlotD, title = "Down Trend Fill", color = #CC0000, transp = 40)
// === /PLOTTING ===
// === STRATEGY ===
// conditions
longCond = crossover(closeSeries, openSeries)
shortCond = crossunder(closeSeries, openSeries)
// entries and base exit
strategy.entry("long", strategy.long, when = longCond)
strategy.entry("short", strategy.short, when = shortCond)
// if we're using the trailing stop
if (useStop)
 strategy.exit("XL", from_entry = "long", trail_points = slPoints, trail_offset = slOffset)
 strategy.exit("XS", from_entry = "short", trail_points = slPoints, trail_offset = slOffset)
// not sure needed, but just incase..
strategy.exit("XL", from_entry = "long", when = shortCond)
strategy.exit("XS", from_entry = "short", when = longCond)
// === /STRATEGY ===

Answer 1

Don't use security() at all. It contains future leak.

Therefore Open Close Cross strategy will never work. Don't be fooled by these exceptional backtest results.

• PeterO: Perhaps it sounds like a comment, but unfortunately it is the best answer to this issue. Definitely should stay here.
• karatedog: I can use security() for what I want, with no issues. It is just reading from a different data source. Its quirks can be learned and avoided or worked around, especially if your aim is to use more than one time frame.

Answer 2

Please read about security function here https://www.tradingview.com/wiki/Context_Switching,The%E2%80%98security%E2%80%99_Function

The security function security(tickerid, timeframe, exp) would calculate the exp on a data, different from main chart symbol.

• rasputin: Please consider the @PeterO's answer below.