Python AttributeError: class object has no attribute

Question

When I try to run the code of a class I'm writing, I get an AttributeError and I'm not sure why. The specific error is as follows:

    self.marker = self.markers[marker[1:]]
AttributeError: 'TTYFigureData' object has no attribute 'markers'

Here is part of the class I'm writing:

class TTYFigureData(object):
    """
    data container of TTYFigure
    """
    def __init__(
        self,
        x,                      # x values
        y,                      # y values
        marker          = "_.", # datum marker
        plot_slope      = True
        ):
        self.x          = x
        self.y          = y
        self.plot_slope = plot_slope
        self.set_marker(marker)
        self.markers = {
            "-" : u"None" ,
            "," : u"\u2219"
        }

    def set_marker(
        self,
        marker
        ):
        if marker in [None, "None", u"None", ""]:
            self.plot_slope = True
            self.marker = ""
        elif marker[0] == "_":
            self.marker = self.markers[marker[1:]]
        else:
            self.marker = marker

Where am I going wrong?

Solution 1

Martijn's answer explains the problem and gives the minimal solution. However, given that self.markers appears to be constant, I would make it a class attribute rather than recreating it for every instance:

class TTYFigureData(object):
    """Data container of TTYFigure."""

    MARKERS = {
        "-": u"None" ,
        ",": u"\u2219",
    }

    def __init__(self, x, y, marker='_.', plot_slope=True):
        """Document parameters here as required."""
        self.x = x
        self.y = y
        self.plot_slope = plot_slope
        self.set_marker(marker)

    def set_marker(self, marker):
        """See also here - usage guidance is also good."""
        if marker in [None, "None", u"None", ""]:
            self.plot_slope = True
            self.marker = ""
        elif marker[0] == "_":
            self.marker = self.MARKERS[marker[1:]]
        else:
            self.marker = marker

(note also changes to style in line with the official guidance)

Solution 2

In your __init__ method, you call self.set_marker() before you set self.markers:

self.set_marker(marker)
self.markers = {
    "-" : u"None" ,
    "," : u"\u2219"
}

So when set_marker() runs, there is no self.markers yet. Move the call down a line:

self.markers = {
    "-" : u"None" ,
    "," : u"\u2219"
}
self.set_marker(marker)