Bump minimum python version to 3.7 (#649)

.azure-pipelines.yml

@@ -11,11 +11,11 @@ jobs:
     vmImage: 'ubuntu-18.04'
   strategy:
     matrix:
-      Python38:
-        python.version: '3.8'
+      Python39:
+        python.version: '3.9'
         RUN_COVERAGE: yes
-      Python36:
-        python.version: '3.6'
+      Python37:
+        python.version: '3.7'
   steps:
   - task: UsePythonVersion@0
     inputs:
@@ -75,8 +75,8 @@ jobs:
 
   - task: UsePythonVersion@0
     inputs:
-      versionSpec: '3.8'
-    displayName: 'Use Python 3.8'
+      versionSpec: '3.9'
+    displayName: 'Use Python 3.9'
 
   - script: |
       python -m pip install --upgrade pip

pyproject.toml

@@ -9,7 +9,7 @@ requires = [
 [project]
 name = "anndata"
 description = "Annotated data."
-requires-python = ">=3.6"
+requires-python = ">=3.7"
 license = {file = "LICENSE"}
 authors = [
     {name = "Philipp Angerer"},
@@ -34,7 +34,6 @@ classifiers = [
     "Operating System :: Microsoft :: Windows",
     "Operating System :: POSIX :: Linux",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.6",
     "Programming Language :: Python :: 3.7",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
@@ -112,5 +111,5 @@ xfail_strict = true
 
 [tool.black]
 line-length = 88
-target-version = ["py36"]
+target-version = ["py37"]
 exclude = "^/build/.*$"