Accessing a method using getattr

Question

When creating a new class instance, I'm trying to call a method in a different class however can't get it to work. Here's what I have:

class DataProject(object):    
    def __init__(self, name=none,input_file=None,datamode=None,comments=None,readnow=True):
        ..............
        # here's where I'm trying to call the method in the other class
        if type(input_file) == str:
            self.input_file_format = self.input_file.split(".")[-1]
            if readnow:
                getattr(Analysis(),'read_'+self.input_file_format)(self,input_file)

class Analysis(object):
    def __init__(self):
        pass # nothing happens here atm

    def read_xlsx(self,parent,input_file):
        """Method to parse xlsx files and dump them into a DataFrame"""
        xl = pd.ExcelFile(input_file)
        for s in sheet_names:
            parent.data[s]=xl.parse(s)

I'm getting a NameError: global name 'read_xlsx' is not defined when I run this with afile.xlxs as input which made me think that I just discovered a massive hole in my Python knowledge (not that there aren't many but they tend to be hard to see, sort of like big forests...).

I would have thought that getattr(Analysis(), ... ) would access the global name space in which it would find the Analysis class and its methods. And in fact print(globals().keys()) shows that Analysis is part of this:

['plt', 'mlab', '__builtins__', '__file__', 'pylab', 'DataProject', 'matplotlib', '__package__', 'W32', 'Helpers', 'time', 'pd', 'pyplot', 'np', '__name__', 'dt', 'Analysis', '__doc__']

What am I missing here?

EDIT:

The full traceback is:

Traceback (most recent call last):
  File "C:\MPython\dataAnalysis\dataAnalysis.py", line 101, in <module>
    a=DataProject(input_file='C:\\MPython\\dataAnalysis\\EnergyAnalysis\\afile.xlxs',readnow=True)
  File "C:\MPython\dataAnalysis\dataAnalysis.py", line 73, in __init__
    getattr(Analysis(),'read_'+self.input_file_format)(self,input_file)
  File "C:\MPython\dataAnalysis\dataAnalysis.py", line 90, in read_xls
    read_xlsx(input_file)
NameError: global name 'read_xlsx' is not defined

My main call is:

if __name__=="__main__":
    a=DataProject(input_file='C:\\MPython\\dataAnalysis\\EnergyAnalysis\\afile.xlx',readnow=True)

Answer 1

From the full traceback, it appears that your DataProject class is calling (successfully) the Analysys.read_xls method, which in turn is trying to call read_xlsx. However, it's calling it as a global function, not as a method.

Probably you just need to replace the code on line 90, turning read_xlsx(input_file) into self.read_xlsx(input_file), though you might need to pass an extra parameter for the parent DataProject instance too.