Developer experience with Pyzed

Speed numbers matter less than how a toolkit feels at 11 pm when you are trying to finish something. This page walks through a Pyzed project from the first command to a packaged app, and compares each step with what the other toolkits ask of you. Where we say “we measured” or “we hit”, it happened while preparing the benchmarks.

1. Install

uv

Windows, macOS and Linux

uv add pyzed-ui

pip

Windows, macOS and Linux

pip install pyzed-ui

python

macOS and Linux

python3 -m pip install pyzed-ui

Windows (PowerShell)

py -m pip install pyzed-ui

One wheel with the Rust core already compiled, for Windows, macOS and Linux, and no runtime dependencies. Compare what we ran into on a clean Ubuntu 24.04 container:

Toolkit	What pip install needed there
Pyzed	Nothing else (a desktop Linux already has the libxkbcommon-x11 library it loads; our bare container did not)
tkinter	Not installable from pip: it comes with Python, or with a python3-tk system package on Debian and Ubuntu
PySide6	Nothing else, but a large download (see install size)
Kivy, Dear PyGui	Nothing else
Flet	flet[desktop]; the desktop client is downloaded the first time an app runs, and on Linux it needed the libsecret and libgles2 system packages
Toga	Failed until we installed libgirepository-2.0-dev and libcairo2-dev with apt, because PyGObject was compiled from source
wxPython	No Linux wheels on PyPI: pip compiles wxWidgets from source (wheels for some distributions are on wxpython.org)

2. First window

uv

Windows, macOS and Linux

uvx --from pyzed-ui pyzed new hello --script
cd hello
uv run --with pyzed-ui main.py

pip

Windows, macOS and Linux

pyzed new hello --script
cd hello
python main.py

python

macOS and Linux

python3 -m pyzed new hello --script
cd hello
python3 main.py

Windows (PowerShell)

py -m pyzed new hello --script
cd hello
py main.py

or a full uv project with linting, type checking and git with pyzed new hello. The app is a class with a view():

import pyzed as pz
from pyzed import ui


class Hello(pz.App):
    title = "Hello"
    name = ""

    def view(self):
        return pz.center(pz.column([
            ui.input(self.name, lambda text: setattr(self, "name", text), placeholder="Your name"),
            ui.heading(f"Hello, {self.name or 'world'}!"),
        ], spacing=12, max_width=320))


pz.run(Hello)

It already has a dark theme, focus rings, hover states and proper text rendering; nothing to style.

How much code?

We wrote the same two apps in every toolkit, in the style of each project’s own documentation (source), and counted the lines that are not blank, comments or docstrings.

Counter (−, + and Reset)lines · lower is better

1. CustomTkinter6.0.014 lines
2. tkinterTk 9.0.315 lines
3. Flet1.0.417 lines
4. Pyzed1.2.019 lines
5. Dear PyGui2.3.119 lines
6. Toga0.5.719 lines
7. PySide6 (Qt)6.12.028 lines
8. Kivy2.3.131 lines

To-do list (add, tick off, delete, count)lines · lower is better

1. Flet1.0.422 lines
2. Dear PyGui2.3.129 lines
3. Pyzed1.2.031 lines
4. CustomTkinter6.0.032 lines
5. Toga0.5.735 lines
6. tkinterTk 9.0.339 lines
7. PySide6 (Qt)6.12.062 lines
8. Kivy2.3.181 lines

Line counts depend on style, so read them as a rough guide. The bigger difference is what the lines do: in tkinter, Qt, Flet and Dear PyGui part of the code copies data into widgets and keeps them in sync; in Pyzed, view() is the only place that turns data into widgets.

3. Hot reload

uv

Windows, macOS and Linux

uv run pyzed dev main.py

pip

Windows, macOS and Linux

pyzed dev main.py

python

macOS and Linux

python3 -m pyzed dev main.py

Windows (PowerShell)

py -m pyzed dev main.py

Edit view(), a helper module or a style and save: the window updates in place, with your data still there (the app object is kept and gets the new class). New methods and new attributes in __init__ show up without restarting, and a changed initial value applies if the app has not changed it (see Hot reload). If the new code fails, the error appears in the window, and the next save that fixes it brings the app back.

Flet restarts the app on save, and NiceGUI reloads its server, so in-memory state starts over. Qt offers a live preview for QML in its tools, not for Python Widgets code. tkinter, Kivy, Dear PyGui and Toga need a restart (or a third-party tool).

4. A visual designer that writes Python

pyzed design opens Pyzed Design: drag components onto a form, set their properties, wire events to Python handlers, edit code with completion and diagnostics (ty and ruff), and run the form.

Qt has the most powerful designers (Qt Designer, Qt Creator, Qt Design Studio). tkinter and wxPython have third-party designers; Kivy, Dear PyGui, Flet, Toga and NiceGUI have none.

5. Autocomplete and type checking

The package is typed (py.typed, with stubs for the Rust core), so editors complete widget arguments and type checkers catch mistakes before you run anything:

ui.button("Save", self.save, variant="solid", size="sm", keys="ctrl-s")
#                            ^ completion lists every option, with its documentation

New projects run ty and ruff with pyzed check.

6. Error messages that say what to fix

Mistakes are caught when the widget is created, with the value that was wrong:

ValueError: unknown button variant 'soild'
ValueError: unknown icon 'plsu'; see pyzed.icons.names()
ValueError: invalid color: "#12345"
TypeError: text() got an unexpected keyword argument 'colr'

An exception inside view() or a callback shows up in the window (with hot reload) or as a normal Python traceback that points at your line, not at the C++ or Rust code underneath.

7. Screenshots and tests without a screen

app = Todo()
app.tasks = [["Write docs", False], ["Ship it", True]]
app.screenshot("todo.png", size=(420, 320))

screenshot renders off-screen with the CPU, so it works in CI and in tests; see Tests and screenshots. Other toolkits need a virtual display (Xvfb) or a screen grabber for the same thing.

8. Packaging

uv

Windows, macOS and Linux

uv run pyzed build             # dist/MyApp (a folder) or --onefile

pip

Windows, macOS and Linux

pyzed build             # dist/MyApp (a folder) or --onefile

python

macOS and Linux

python3 -m pyzed build             # dist/MyApp (a folder) or --onefile

Windows (PowerShell)

py -m pyzed build             # dist/MyApp (a folder) or --onefile

pyzed build wraps PyInstaller and fills in what forms load at runtime. Elsewhere: Qt has pyside6-deploy (Nuitka), Flet’s flet build needs the Flutter SDK, Toga uses Briefcase (very good, and it also targets phones), Kivy uses Buildozer for Android and PyInstaller for desktop. See Build and distribute.

9. Working with AI assistants

Language models write better code for APIs they can look up. Pyzed gives them:

• an MCP server with the exact signature of every widget, the docs, code checks and screenshots of the result, so an agent in Claude Code, Cursor, VS Code or Zed can see what it built;
• this documentation as plain text in llms.txt;
• the designer’s Agent panel, which edits forms with you;
• pyzed.agents to put models with tools inside your own app.

Flet also publishes an MCP server; Qt offers Qt AI Assistant in Qt Creator (commercial, aimed at C++ and QML).