Fix use of importlib.metadata and unify requirements.txt (#8)

* Fix importlib usage and unify requirements.txt

* Remove requirements-37.txt

* Add a test matrix to additionally test against 3.7

.github/workflows/test.yaml

@@ -21,6 +21,12 @@ on: [push, pull_request]
 jobs:
   test:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version:
+          - "3.7"
+          - "3.10"
     steps:
       - uses: actions/checkout@v2
       - name: Setup Rust toolchain
@@ -40,13 +46,14 @@ jobs:
           key: target-maturin-cache-
       - uses: actions/setup-python@v2
         with:
-          python-version: "3.10"
+          python-version: ${{ matrix.python-version }}
       - name: Create Virtualenv
         run: |
           python -m venv venv
           source venv/bin/activate
           pip install -r requirements.txt
       - name: Run Linters
+        if: ${{ matrix.python-version == '3.10' }}
         run: |
           source venv/bin/activate
           flake8 --exclude venv --ignore=E501

README.md

@@ -140,9 +140,7 @@ python3 -m venv venv
 source venv/bin/activate
 # update pip itself if necessary
 python -m pip install -U pip
-# if python -V gives python 3.7
-python -m pip install -r requirements-37.txt
-# if python -V gives python 3.8/3.9/3.10
+# install dependencies
 python -m pip install -r requirements.txt
 ```
 
@@ -161,9 +159,6 @@ To change test dependencies, change the `requirements.in` and run
 ```bash
 # install pip-tools (this can be done only once), also consider running in venv
 python -m pip install pip-tools
-
-# change requirements.in and then run
-python -m piptools compile --generate-hashes -o requirements-37.txt
 # or run this is you are on python 3.8/3.9/3.10
 python -m piptools compile --generate-hashes -o requirements.txt
 ```

datafusion/__init__.py

@@ -18,7 +18,12 @@
 from abc import ABCMeta, abstractmethod
 from typing import List
 
-import importlib.metadata
+try:
+    import importlib.metadata as importlib_metadata
+except ImportError:
+    import importlib_metadata
+
+
 import pyarrow as pa
 
 from ._internal import (
@@ -30,7 +35,7 @@
 )
 
 
-__version__ = importlib.metadata.version("datafusion")
+__version__ = importlib_metadata.version(__name__)
 
 
 __all__ = [