Trouble with "from…import…as"

[arbiel]

Hi

Trying to understand how to use "from…import…as"

I recorded in "test.py" this extract from a script I'm presently coding

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#!/usr/bin/env python # -*- coding: utf-8 -*- import sys from html.parser import HTMLParser from unicodedata import name as ucd_nom from unicodedata import lookup as ucd_car #import xml.etree.ElementTree from xml.etree.ElementTree import ElementTree as arbre from xml.etree.ElementTree import Element as xml   def le_fichier_xml():     """Table de correspondance."""     return '/home/remi/Documents/programmation/python/grec_vocab/alphabet.xml' le_fichier_xml() larbre=arbre() alphabet=larbre.parse(le_fichier_xml()) for elem in list(alphabet):     print(elem.tag, elem.attrib)

No problem when I run it

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remi@remi-Vostro-3550:~$ python '/home/remi/Documents/programmation/python/test.py' div {'id': 'simples'} div {'id': 'combinées'} remi@remi-Vostro-3550:~$

If I skip the line 15:

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#!/usr/bin/env python # -*- coding: utf-8 -*- import sys from html.parser import HTMLParser from unicodedata import name as ucd_nom from unicodedata import lookup as ucd_car #import xml.etree.ElementTree from xml.etree.ElementTree import ElementTree as arbre from xml.etree.ElementTree import Element as xml   def le_fichier_xml():     """Table de correspondance."""     return '/home/remi/Documents/programmation/python/grec_vocab/alphabet.xml' le_fichier_xml() #larbre=arbre() #alphabet=larbre.parse(le_fichier_xml()) alphabet=arbre.parse(le_fichier_xml()) for elem in list(alphabet):     print(elem.tag, elem.attrib)

it does not run any longer

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remi@remi-Vostro-3550:~$ python '/home/remi/Documents/programmation/python/test.py' Traceback (most recent call last):   File "/home/remi/Documents/programmation/python/test.py", line 17, in <module>     alphabet=arbre.parse(le_fichier_xml()) TypeError: parse() missing 1 required positional argument: 'source' Error in sys.excepthook: Traceback (most recent call last):   File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in apport_excepthook     from apport.fileutils import likely_packaged, get_recent_crashes   File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in <module>     from apport.report import Report   File "/usr/lib/python3/dist-packages/apport/report.py", line 30, in <module>     import apport.fileutils   File "/usr/lib/python3/dist-packages/apport/fileutils.py", line 23, in <module>     from apport.packaging_impl import impl as packaging   File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 24, in <module>     import apt   File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in <module>     import apt_pkg ModuleNotFoundError: No module named 'apt_pkg'   Original exception was: Traceback (most recent call last):   File "/home/remi/Documents/programmation/python/test.py", line 17, in <module>     alphabet=arbre.parse(le_fichier_xml()) TypeError: parse() missing 1 required positional argument: 'source' remi@remi-Vostro-3550:~$

with an error

Error:
TypeError: parse() missing 1 required positional argument: 'source'

not quite clear, as the python documentation reads

parse(source, parser=None)

Loads an external XML section into this element tree. source is a file name or file object. parser is an optional parser instance. If not given, the standard XMLParser parser is used. Returns the section root element.

and I however passed a positional parameter.

So, I'm quite confused

Arbiel

[stullis]

The argument you passed in was assigned to a different parameter. When a method is called, such as ElementTree.parse(), there is an additional parameter often not mentioned in the documentation:

1	class ElementTree(self, source, parser=None):

If you've already learned how to write classes and methods, that should look familiar. The self parameter is intended to be filled by the instantiated object itself (hence the naming convention). When line 15 is omitted, no object is instantiated - there is no self. So, the interpreter fills in the parameters starting from left to right. The argument passed in becomes "self" and there's nothing left for source.

[arbiel]

Hi stullis

This is very clear.

In fact, I did really know what type of object results from «import». I am quite illiterate in terms of object oriented programming (and in lot of other domains also, even if I'm still older than what the Beatles sung). I'm learning by trying, and searching through the documentation.

I modified line 17 with :

1	alphabet=arbre.parse(arbre,le_fichier_xml())

and it works.

It is however, I suppose, better to instantiate the object first and to use it later on.

Thank you.

Arbiel