Picture by WriterOnce we speak about Python, we frequently consider using it to carry out information evaluation or construct a machine studying mannequin. It’s much less frequent to debate creating full net functions with Python exterior of straightforward prototypes utilizing libraries similar to Streamlit or Taipy.
Nonetheless, a library known as Reflex affords net utility improvement options that compete with these of different programming languages. Totally in Python, this open-source library helps customers construct something from small information science apps to massive, multi-page web sites. With robust flexibility but intuitive Python code, we will simply scale net improvement to go well with our wants with Reflex.
On this article, we’ll be taught the fundamentals of constructing a pure Python net utility with Reflex.
Constructing Net Apps with Reflex
On this tutorial, we’ll evaluate the requirements for constructing an internet utility with Reflex. For greatest practices, it’s advisable to make use of a digital atmosphere to keep away from disrupting the general atmosphere.
With this in thoughts, we’ll start growing our Reflex net utility by putting in the Reflex library utilizing the code under:
We are going to then take a look at Reflex by creating a brand new undertaking and initiating a brand new utility. Use the next code, however change the test_app folder title to your individual.
mkdir test_app
cd test_app
reflex init
The code above prompts you with questions on whether or not you wish to create the undertaking with a pre-made template or not.
For this tutorial, choose the clean Reflex app, and you will notice the brand new undertaking construction created, just like the one under.
Run the next command to see in case your Reflex utility runs correctly:
Go to the native URL serving the applying. If it really works nicely, you will notice one thing just like the picture under:
That is the fundamental net utility scaffold generated by Reflex. We are going to construct one thing extra subtle later, however we’ll begin with the basics.
Let’s begin by understanding the parts used to construct the net utility within the Reflex library. First, open
test_app.py and exchange its contents with the next code:
import reflex as rx
class State(rx.State):
depend: int = 0
def increment(self):
self.depend += 1
def decrement(self):
self.depend -= 1
def index():
return rx.hstack(
rx.button(
"Decrement",
color_scheme="ruby",
on_click=State.decrement,
),
rx.heading(State.depend, font_size="2em"),
rx.button(
"Increment",
color_scheme="grass",
on_click=State.increment,
),
spacing="4",
)
app = rx.App()
app.add_page(index)
This may present a web site just like the one under.
Let’s break down what’s occurring within the code above.
First, we outline the state, which incorporates variables (known as vars) and features (known as occasion handlers) that may change the state of the applying.
For instance, we outline a single variable known as depend that holds an integer with an preliminary worth of 0.
class State(rx.State):
depend: int = 0
Then we’ve got occasion handlers—features inside the state that modify variables in response to consumer actions. Within the code above, we outline the occasion handlers as follows:
def increment(self):
self.depend += 1
def decrement(self):
self.depend -= 1
Subsequent, we outline the net utility UI as follows:
def index():
return rx.hstack(
rx.button(
"Decrement",
color_scheme="ruby",
on_click=State.decrement,
),
rx.heading(State.depend, font_size="2em"),
rx.button(
"Increment",
color_scheme="grass",
on_click=State.increment,
),
spacing="4",
)
The features above outline the net utility interface and use the next parts to construct the UI:
rx.hstack: used to stack parts horizontallyrx.button: used to indicate a button that triggers an occasion when clickedrx.heading: used to indicate textual content in numerous sizes
As you’ll be able to see within the code above, the heading element references the depend variable within the state, and every button triggers a perform within the state when clicked.
There are lots of extra parts you should utilize to construct the net utility; see the Reflex parts documentation.
Lastly, we outline the applying and add the parts to the bottom route with the next code:
app = rx.App()
app.add_page(index)
That may be a easy clarification of the necessary parts that Reflex makes use of to construct an internet utility.
With the reason above completed, let’s construct a barely extra superior net utility with Reflex. Within the instance under, we’ll develop a to-do checklist utility that we will fill and take away objects from.
import uuid
import reflex as rx
from typing import Any, Dict, Listing
class TodoState(rx.State):
todos: Listing[Dict[str, Any]] = []
new_text: str = ""
current_filter: str = "all" # Choose between "all", "lively", "completed"
# Derived values (computed from state)
@rx.var
def items_left(self) -> int:
return sum(1 for t in self.todos if not t["done"])
@rx.var
def items_left_label(self) -> str:
return "1 merchandise left" if self.items_left == 1 else f"{self.items_left} objects left"
@rx.var
def filtered_todos(self) -> Listing[Dict[str, Any]]:
if self.current_filter == "lively":
return [t for t in self.todos if not t["done"]]
if self.current_filter == "completed":
return [t for t in self.todos if t["done"]]
return self.todos
# Occasions (mutate state)
@rx.occasion
def set_new_text(self, worth: str):
self.new_text = (worth or "").strip()
@rx.occasion
def add_todo(self):
textual content = (self.new_text or "").strip()
if not textual content:
return
self.todos.append({"id": str(uuid.uuid4()), "textual content": textual content, "completed": False})
self.new_text = ""
@rx.occasion
def toggle(self, todo_id: str):
for t in self.todos:
if t["id"] == todo_id:
t["done"] = not t["done"]
break
@rx.occasion
def take away(self, todo_id: str):
self.todos = [t for t in self.todos if t["id"] != todo_id]
@rx.occasion
def clear_completed(self):
self.todos = [t for t in self.todos if not t["done"]]
@rx.occasion
def set_filter(self, title: str):
if title in {"all", "lively", "completed"}:
self.current_filter = title
def filter_button(title: str, label: str) -> rx.Part:
return rx.button(
label,
measurement="2",
variant=rx.cond(TodoState.current_filter == title, "strong", "delicate"),
background_color=rx.cond(
TodoState.current_filter == title, "blue.600", "grey.700"
),
shade="white",
_hover={"background_color": "blue.500"},
on_click=lambda: TodoState.set_filter(title),
)
def render_todo_item(todo: rx.Var[dict]) -> rx.Part:
return rx.hstack(
rx.checkbox(
is_checked=todo["done"],
on_change=lambda _: TodoState.toggle(todo["id"]),
measurement="2",
color_scheme="blue",
),
rx.textual content(
todo["text"],
flex="1",
shade=rx.cond(todo["done"], "grey.500", "white"),
text_decoration=rx.cond(todo["done"], "line-through", "none"),
),
rx.icon_button(
"trash",
color_scheme="purple",
variant="delicate",
on_click=lambda: TodoState.take away(todo["id"]),
),
align="middle",
spacing="3",
width="100%",
)
def todo_input_bar() -> rx.Part:
return rx.hstack(
rx.enter(
placeholder="What must be completed?",
worth=TodoState.new_text,
on_change=TodoState.set_new_text,
flex="1",
measurement="3",
background_color="grey.800",
shade="white",
border_color="grey.600",
_placeholder={"shade": "grey.400"},
),
rx.button(
"Add",
measurement="3",
background_color="blue.600",
shade="white",
_hover={"background_color": "blue.500"},
on_click=TodoState.add_todo,
),
spacing="3",
width="100%",
)
def todo_list_panel() -> rx.Part:
return rx.vstack(
rx.foreach(TodoState.filtered_todos, render_todo_item),
spacing="2",
width="100%",
)
def footer_bar() -> rx.Part:
return rx.hstack(
rx.textual content(TodoState.items_left_label, measurement="2", shade="grey.300"),
rx.hstack(
filter_button("all", "All"),
filter_button("lively", "Energetic"),
filter_button("completed", "Carried out"),
spacing="2",
),
rx.button(
"Clear Accomplished",
variant="delicate",
background_color="grey.700",
shade="white",
_hover={"background_color": "grey.600"},
on_click=TodoState.clear_completed,
),
justify="between",
align="middle",
width="100%",
)
def index() -> rx.Part:
return rx.middle(
rx.card(
rx.vstack(
rx.heading("Reflex To-Do", measurement="6", shade="white"),
todo_input_bar(),
rx.separator(border_color="grey.700"),
todo_list_panel(),
rx.separator(margin_y="2", border_color="grey.700"),
footer_bar(),
width="min(720px, 92vw)",
spacing="4",
),
measurement="4",
width="min(760px, 96vw)",
shadow="lg",
background_color="grey.900",
),
min_h="100vh",
padding_y="8",
background_color="black",
)
app = rx.App()
app.add_page(index, route="https://www.kdnuggets.com/", title="Reflex To-Do")
The results of the applying will seem like the picture under.
Within the code above, the movement basically works as follows:
- The app retains a small reminiscence: your duties, what you’re typing, and which filter is chosen.
- You sort within the field and that textual content is saved as you sort.
- You press “Add” and the duty is saved (with an id) and the field clears.
- The checklist immediately refreshes to indicate what’s in reminiscence.
- Every activity row has a checkbox and a trash icon. Checking toggles completion; the trash removes the duty.
- The three filter buttons (All / Energetic / Carried out) change which duties are seen.
- The footer reveals what number of duties usually are not completed and allows you to “Clear Accomplished”.
A couple of necessary distinctions—past the fundamental parts lined earlier—embody:
- Adorn with
@rx.occasionto declare occasions inside the state. - Adorn with
@rx.varto create derived variables within the state. - Use
rx.Partsignatures when constructing reusable UI helpers to your Reflex utility.
That’s the fundamental clarification and instance of how Reflex works. Attempt it your self and construct the net utility you want with pure Python.
Conclusion
Reflex is an open-source library that permits us to construct net functions in pure Python with a easy but intuitive code sample. Its simple setup and easy-to-understand code enable customers to maintain the logic and UI in a single place. It’s a helpful library for newcomers {and professional} builders alike who wish to construct an utility with Python.
I hope this has helped!
Cornellius Yudha Wijaya is a knowledge science assistant supervisor and information author. Whereas working full-time at Allianz Indonesia, he likes to share Python and information suggestions by way of social media and writing media. Cornellius writes on quite a lot of AI and machine studying subjects.