Markdown finished up to part 1

first_django_app.md

@@ -76,3 +76,67 @@ polls/
     views.py
 ```
 
+## Write the first view
+
+### Step 1: Create a simple view of `polls` app
+
+modify `polls/views.py` as
+
+```python
+from django.http import request
+from django.shortcuts import render
+
+def index(request):
+    return HttpResponse("Hello, world. You're at the polls index")
+```
+
+* `def index(request):...` is the simplest view
+
+### Step 2: In `polls` app, map the URL to this view
+
+After creating a view, map it to a URL so we can call it. Create `polls/urls.py`, and setup mapping `urlpatterns`
+
+```python
+from django.urls import path
+
+from . import views
+
+urlpatterns = [
+    path('', views.index, name='index'),
+]
+```
+
+### Step 3: Point the root URLconf for polls
+
+To point the root URLconf at `polls.urls` module:
+1. In `mysite/urls.py`
+   1. add import for `django.urls.inclue`
+   2. insert a `include()` in `urlpatterns` list
+
+i.e.
+
+```python
+from django.contrib import admin
+from django.urls import include, path
+
+urlpatterns = [
+    path('polls/', include('polls.urls')),
+    path('admin/', admin.site.urls),
+]
+```
+
+#### django.urls.include()
+
+> django.urls.include(): A function that takes a full Python import path to another URLconf module that should be “included” in this place.
+
+* new imported `include()` function allows referencing other URLconfs.
+* `'polls.urls'` is the package that we are using, hence `mysite` can connect to `polls` app
+
+#### path()
+
+Here `path()` function is passed **route** and **view**; two additional option available **kwargs**, and **name**
+
+* `path()` argument **route**: a string that contains a URL pattern. When Django processing a request, it starts at the first pattern in `urlpatterns` and go down the list, comparing requested URL against each pattern
+* `path()` argument **view**: when Django finds a matching pattern, it calls specified view function (a `HttpRequest` obj as the 1st argument, and others captured values as keyword argument)
+* `path()` argument **kwargs**: passed in a dictionary to the target view
+* `path()` argument **name**: naming URL, so we can refer to it elsewhere.