Using classes, functions or other objects from an installed package

Question

I successfully installed this package using pip:

pip install functional-dependencies

Output:

Collecting functional-dependencies
  Downloading functional_dependencies-1.3.0-py2.py3-none-any.whl (33 kB)
Installing collected packages: functional-dependencies
Successfully installed functional-dependencies-1.3.0

which should provide tools for functional dependencies (FDs).

However, trying to get FDs using the commands as per the documentation results in an error:

Python 3.10.7 (tags/v3.10.7:6cc6b13, Sep  5 2022, 14:08:36) [MSC v.1933 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> fd1 = FD("CustomerID", "DateOfBirth")
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    NameError: name 'FD' is not defined

How can I access the classes, functions and objects from the installed package?

The pypi page of the package you are using links to an [example notebook](https://mybinder.org/v2/gl/oer%2Fcs%2Ffunctional-dependencies/HEAD?filepath=notebooks%2FCodd-3NF-ex.ipynb). Note that this package is not about finding FDs but rather normalizing a schema. You can instead try looking at [FDTool](https://github.com/USEPA/FDTool) (not maintained since 3 years or so) although I'd advice you to simply find the FDs as per the duplicates of your previous question. — Abdul Aziz Barkat, Oct 21 '22 at 04:39

score 3 · Accepted Answer · answered Oct 21 '22 at 07:06

Although this is a very basic question, just because the official documentation does not include full working examples, I will provide an answer here.

You have already installed the module functional-dependencies. To use it, you'll need to know the module name to use to import. This is written in the first line of the introduction:

The module functional_dependencies defines the classes FD, FDSet, and RelSchema to represent a single functional dependency (FD), a set of FDs, and a relation schema, respectively.

So, you'll start by doing:

import functional_dependencies

or

from functional_dependencies import *

The latter is generally not recommended because of namespace pollution, but since you probably want to copy-paste examples from the documentation, this will be easier.

Now you can do:

from functional_dependencies import *

fd1 = FD("CustomerID", "DateOfBirth")
fd1.isrminimal()

Otherwise you would have to include the module name to access the classes:

import functional_dependencies

fd1 = functional_dependencies.FD("CustomerID", "DateOfBirth")
fd1.isrminimal()

Now, for the rest of your journey, reading the documentation should be helpful. Other tricks that might be useful is typing help(functional_dependencies) in the Python interpreter. It will print all functions and classes that are defined in the module, including the available documentation. You can also do this on an object: help(fd1) would print help about the object. You can also execute dir(fd1) to see which attributes the object has, which includes all its methods.

Using classes, functions or other objects from an installed package

1 Answers1