Picture by CreatorOnce we speak about Python, we frequently consider using it to carry out knowledge evaluation or construct a machine studying mannequin. It’s much less widespread to debate creating full net functions with Python exterior of easy prototypes utilizing libraries comparable to Streamlit or Taipy.
Nonetheless, a library known as Reflex provides net utility growth options that compete with these of different programming languages. Totally in Python, this open-source library helps customers construct something from small knowledge science apps to massive, multi-page web sites. With robust flexibility but intuitive Python code, we will simply scale net growth 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 setting to keep away from disrupting the general setting.
With this in thoughts, we’ll start creating our Reflex net utility by putting in the Reflex library utilizing the code beneath:
We are going to then check Reflex by creating a brand new venture 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 venture with a pre-made template or not.
For this tutorial, choose the clean Reflex app, and you will note the brand new venture construction created, just like the one beneath.
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 effectively, you will note one thing just like the picture beneath:
That is the essential 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 elements 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 can present an internet site just like the one beneath.
Let’s break down what’s occurring within the code above.
First, we outline the state, which incorporates variables (known as vars) and capabilities (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—capabilities inside the state that modify variables in response to person 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 capabilities above outline the net utility interface and use the next elements 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 varied sizes
As you may see within the code above, the heading element references the depend variable within the state, and every button triggers a operate within the state when clicked.
There are various extra elements you should use to construct the net utility; see the Reflex elements documentation.
Lastly, we outline the applying and add the elements to the bottom route with the next code:
app = rx.App()
app.add_page(index)
That may be a easy rationalization of the vital elements that Reflex makes use of to construct an internet utility.
With the reason above carried out, let’s construct a barely extra superior net utility with Reflex. Within the instance beneath, we’ll develop a to-do record utility that we will fill and take away objects from.
import uuid
import reflex as rx
from typing import Any, Dict, Record
class TodoState(rx.State):
todos: Record[Dict[str, Any]] = []
new_text: str = ""
current_filter: str = "all" # Choose between "all", "energetic", "carried out"
# 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) -> Record[Dict[str, Any]]:
if self.current_filter == "energetic":
return [t for t in self.todos if not t["done"]]
if self.current_filter == "carried out":
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, "carried out": 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", "energetic", "carried out"}:
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, "stable", "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="pink",
variant="delicate",
on_click=lambda: TodoState.take away(todo["id"]),
),
align="heart",
spacing="3",
width="100%",
)
def todo_input_bar() -> rx.Part:
return rx.hstack(
rx.enter(
placeholder="What must be carried out?",
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("energetic", "Lively"),
filter_button("carried out", "Performed"),
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="heart",
width="100%",
)
def index() -> rx.Part:
return rx.heart(
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 beneath.
Within the code above, the stream 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 record immediately refreshes to indicate what’s in reminiscence.
- Every process row has a checkbox and a trash icon. Checking toggles completion; the trash removes the duty.
- The three filter buttons (All / Lively / Performed) change which duties are seen.
- The footer exhibits what number of duties will not be carried out and allows you to “Clear Accomplished”.
Just a few vital distinctions—past the essential elements lined earlier—embody:
- Beautify with
@rx.occasionto declare occasions inside the state. - Beautify with
@rx.varto create derived variables within the state. - Use
rx.Partsignatures when constructing reusable UI helpers in your Reflex utility.
That’s the primary rationalization and instance of how Reflex works. Strive it your self and construct the net utility you want with pure Python.
Conclusion
Reflex is an open-source library that enables us to construct net functions in pure Python with a easy but intuitive code sample. Its easy setup and easy-to-understand code permit 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 knowledge author. Whereas working full-time at Allianz Indonesia, he likes to share Python and knowledge suggestions through social media and writing media. Cornellius writes on quite a lot of AI and machine studying matters.
