PyQT QwtScaleDiv adds ticks to axis

[mbernasocchi]

Hi, i'm implementing my own QwtScaleDraw like that:

class TimeScaleDraw(QwtScaleDraw):
    def __init__(self, baseTime):
        QwtScaleDraw.__init__(self)
        #QTime baseTime
        self.baseTime = baseTime
        self.setLabelAlignment(Qt.AlignLeft | Qt.AlignBottom)
        self.setLabelRotation(-25.0)
 
    def label(self, secs):
        upTime = self.baseTime.addSecs(secs)
        upTime = upTime.toString('dd MM yy hh:mm:ss')
        return QwtText(upTime)

class TimeScaleDraw(QwtScaleDraw):
    def __init__(self, baseTime):
        QwtScaleDraw.__init__(self)
        #QTime baseTime
        self.baseTime = baseTime
        self.setLabelAlignment(Qt.AlignLeft | Qt.AlignBottom)
        self.setLabelRotation(-25.0)

    def label(self, secs):
        upTime = self.baseTime.addSecs(secs)
        upTime = upTime.toString('dd MM yy hh:mm:ss')
        return QwtText(upTime)

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then I use it this way:

ticks = [0, 60, 120]
div = QwtScaleDiv()
div.setInterval(ticks[0], ticks[len(ticks)-1])
div.setTicks(QwtScaleDiv.MinorTick, [])
div.setTicks(QwtScaleDiv.MediumTick, [])
div.setTicks(QwtScaleDiv.MajorTick, ticks)
draw = TimeScaleDraw(QDateTime(self.main.timeMin))
draw.setScaleDiv(div)
self.plot.setAxisScaleDraw(QwtPlot.xBottom, draw)
self.plot.setAxisScale(QwtPlot.yLeft, self.main.valueMin, self.main.valueMax)

ticks = [0, 60, 120]
div = QwtScaleDiv()
div.setInterval(ticks[0], ticks[len(ticks)-1])
div.setTicks(QwtScaleDiv.MinorTick, [])
div.setTicks(QwtScaleDiv.MediumTick, [])
div.setTicks(QwtScaleDiv.MajorTick, ticks)
draw = TimeScaleDraw(QDateTime(self.main.timeMin))
draw.setScaleDiv(div)
self.plot.setAxisScaleDraw(QwtPlot.xBottom, draw)
self.plot.setAxisScale(QwtPlot.yLeft, self.main.valueMin, self.main.valueMax)

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I'd like to have only 3 ticks (where there actually are values) on my x axis, but some how I get more ticks added (see screen shot). what do i do wrong? any suggestion?