NoReverseMatch at / error in Django

Question

I have started to display blog posts on my homepage and making it so you can read the full post when I click the anchor link but when refresh I get a "NoReverseMatch at /" error.

Here my main urls.py:

from django.conf.urls import url, include
from django.contrib import admin

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^$', include("blog.urls"))
]

blog/urls.py:

from django.conf.urls import url
from . import views

urlpatterns = [
    url(r'^$', views.post_list, name='post_list'),
    url(r'^post/(?P<pk>\d+)/$', views.post_detail, name='post_detail'),
]

blog/views.py

from django.shortcuts import render, get_object_or_404
from django.utils import timezone
from .models import Post

def post_list(request):
    posts = Post.objects.filter(published_date__lte=timezone.now()).order_by('published_date')
    return render(request, "blog/post_list.html", {"posts": posts})

def post_detail(request, pk):
  post = get_object_or_404(Post, pk=pk)
  return render(request, 'blog/post_detail.html', {'post': post})

and the html file that seems to be linked with the error (blog/post_detail.html):

{% extends 'blog/base.html' %}

{% block content %}
    {% for post in posts %}
        <div class="post">
            <div class="date">
                {{ post.published_date }}
            </div>
            <h1><a href="{% url 'post_detail' pk=post.pk %}">{{ post.title }}</a></h1>
            <p>{{ post.text|linebreaksbr }}</p>
        </div>
    {% endfor %}
{% endblock %}