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?

Your code style is somewhat... idiosyncratic ("awful" seemed a bit pejorative), which makes it hard to follow. Note, though, that you call self.set_marker before initialising self.markers. Given that self.markers appears to be fixed, why not make it a class attribute? — jonrsharpe
– jonrsharpe, Commented Sep 28, 2015 at 13:12
Please do post a full traceback for Python errors. For this case, for example, the fact that set_marker() is called from __init__ is a crucial clue as to what is going wrong, the traceback would show that. — Martijn Pieters
– Martijn Pieters, Commented Sep 28, 2015 at 13:15
@jonsharpe Ah, that's it! Well spotted. Thanks for looking. The code is rough and I know the approach of having a new line for each function argument is not considered standard. Is the approach really so bad, particularly for large numbers of arguments? — d3pd
– d3pd, Commented Sep 28, 2015 at 13:15
@d3pd: yes, it made it very hard to distinguish between argument list and method body, for example. Please do read the Python styleguide, which offers better alternatives. — Martijn Pieters
– Martijn Pieters, Commented Sep 28, 2015 at 13:16

Martijn Pieters · Accepted Answer · 2015-09-28 13:13:46Z

6

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)

answered Sep 28, 2015 at 13:13

Martijn Pieters

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1 Comment

d3pd Over a year ago

Thank you very much for your clear solution. It was a silly thing to miss.

Community · Accepted Answer · 2017-05-23 12:22:23Z

3

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)

edited May 23, 2017 at 12:22

CommunityBot

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answered Sep 28, 2015 at 13:22

jonrsharpe

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1 Comment

d3pd Over a year ago

Thank you for your clear solution and for your guidance on changing the markers attribute from an instance attribute to a class attribute.

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