Picture by CreatorAfter we speak about Python, we frequently consider using it to carry out information evaluation or construct a machine studying mannequin. It’s much less widespread to debate creating full net purposes with Python exterior of straightforward prototypes utilizing libraries resembling Streamlit or Taipy.
Nonetheless, a library known as Reflex presents net software growth 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 sturdy flexibility but intuitive Python code, we will simply scale net growth to swimsuit our wants with Reflex.
On this article, we are going to study the fundamentals of constructing a pure Python net software with Reflex.
Constructing Internet Apps with Reflex
On this tutorial, we are going to evaluate the requirements for constructing an online software with Reflex. For finest practices, it’s advisable to make use of a digital surroundings to keep away from disrupting the general surroundings.
With this in thoughts, we are going to start growing our Reflex net software by putting in the Reflex library utilizing the code under:
We’ll then take a look at Reflex by creating a brand new challenge and initiating a brand new software. 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 need to create the challenge with a pre-made template or not.
For this tutorial, choose the clean Reflex app, and you will notice the brand new challenge construction created, just like the one under.
Run the next command to see in case your Reflex software runs correctly:
Go to the native URL serving the appliance. If it really works effectively, you will notice one thing just like the picture under:
That is the fundamental net software scaffold generated by Reflex. We’ll 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 software within the Reflex library. First, open
test_app.py and change 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 an internet 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 capabilities (known as occasion handlers) that may change the state of the appliance.
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 throughout 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 software 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 software interface and use the next parts to construct the UI:
rx.hstack: used to stack components horizontallyrx.button: used to point out a button that triggers an occasion when clickedrx.heading: used to point out textual content in varied sizes
As you possibly can see within the code above, the heading part references the depend variable within the state, and every button triggers a perform within the state when clicked.
There are numerous extra parts you need to use to construct the net software; see the Reflex parts documentation.
Lastly, we outline the appliance and add the parts to the bottom route with the next code:
app = rx.App()
app.add_page(index)
That could be a easy rationalization of the vital parts that Reflex makes use of to construct an online software.
With the reason above accomplished, let’s construct a barely extra superior net software with Reflex. Within the instance under, we are going to develop a to-do record software 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", "lively", "accomplished"
# 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 == "lively":
return [t for t in self.todos if not t["done"]]
if self.current_filter == "accomplished":
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, "accomplished": 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", "accomplished"}:
self.current_filter = title
def filter_button(title: str, label: str) -> rx.Part:
return rx.button(
label,
dimension="2",
variant=rx.cond(TodoState.current_filter == title, "stable", "gentle"),
background_color=rx.cond(
TodoState.current_filter == title, "blue.600", "grey.700"
),
colour="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"]),
dimension="2",
color_scheme="blue",
),
rx.textual content(
todo["text"],
flex="1",
colour=rx.cond(todo["done"], "grey.500", "white"),
text_decoration=rx.cond(todo["done"], "line-through", "none"),
),
rx.icon_button(
"trash",
color_scheme="purple",
variant="gentle",
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 accomplished?",
worth=TodoState.new_text,
on_change=TodoState.set_new_text,
flex="1",
dimension="3",
background_color="grey.800",
colour="white",
border_color="grey.600",
_placeholder={"colour": "grey.400"},
),
rx.button(
"Add",
dimension="3",
background_color="blue.600",
colour="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, dimension="2", colour="grey.300"),
rx.hstack(
filter_button("all", "All"),
filter_button("lively", "Energetic"),
filter_button("accomplished", "Performed"),
spacing="2",
),
rx.button(
"Clear Accomplished",
variant="gentle",
background_color="grey.700",
colour="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", dimension="6", colour="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",
),
dimension="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 appliance will appear to be the picture under.
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 point out what’s in reminiscence.
- Every job row has a checkbox and a trash icon. Checking toggles completion; the trash removes the duty.
- The three filter buttons (All / Energetic / Performed) change which duties are seen.
- The footer exhibits what number of duties usually are not accomplished and allows you to “Clear Accomplished”.
Just a few vital distinctions—past the fundamental parts lined earlier—embrace:
- Enhance with
@rx.occasionto declare occasions throughout the state. - Enhance with
@rx.varto create derived variables within the state. - Use
rx.Partsignatures when constructing reusable UI helpers to your Reflex software.
That’s the primary rationalization and instance of how Reflex works. Attempt it your self and construct the net software you want with pure Python.
Conclusion
Reflex is an open-source library that permits us to construct net purposes in pure Python with a easy but intuitive code sample. Its easy 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 need to construct an software 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.
