tkinter : simple marshmallow demo.

About the marshmallow package

• It checks if your data has the correct fields.
• It verifies that each field has the right type.
• It helps you validate JSON before using it.
• It can convert Python data into clean JSON.

About your this source code:

• It loads the marshmallow package when the app starts.
• It reads the JSON you type in the input box.
• It tries to convert that text into Python data.
• It validates the data using your marshmallow schema.
• It shows the result or the error directly in the output box.
• It does not use print or message boxes.

Why this tool is useful

• You can test JSON visually.
• You can see validation errors instantly.
• You avoid console output.
• You keep everything inside the GUI.

Let's see the sourve code:

import json
import tkinter as tk
from tkinter import ttk

# ------------------ Package Load Test ------------------

try:
    from marshmallow import Schema, fields, ValidationError
    package_status = "Package marshmallow loaded successfully."
except Exception as e:
    package_status = "PACKAGE LOAD ERROR: " + str(e)


# ------------------ Marshmallow Schema ------------------

class PersonSchema(Schema):
    full_name = fields.Str(required=True)
    city = fields.Str(required=True)
    birth_date = fields.Date(required=True)
    nicknames = fields.List(fields.Str(), required=True)


schema = PersonSchema()


# ------------------ Tkinter UI ------------------

def process_json():
    raw = editor.get("1.0", tk.END).strip()

    output.delete("1.0", tk.END)

    # Step 1: package status
    output.insert(tk.END, package_status + "\n\n")

    # Step 2: show raw JSON
    output.insert(tk.END, "RAW JSON RECEIVED:\n" + raw + "\n\n")

    # Step 3: JSON parsing
    try:
        data = json.loads(raw)
        output.insert(tk.END, "JSON PARSED OK.\n\n")
    except Exception as e:
        output.insert(tk.END, "JSON ERROR:\n" + str(e))
        return

    # Step 4: Marshmallow validation
    try:
        result = schema.dump(data)
        output.insert(tk.END, "SCHEMA VALIDATION OK.\n\n")
    except ValidationError as e:
        output.insert(tk.END, "SCHEMA ERROR:\n" + json.dumps(e.messages, indent=2))
        return

    # Step 5: Final result
    output.insert(tk.END, "FINAL RESULT:\n" + json.dumps(result, indent=2))


root = tk.Tk()
root.title("Marshmallow Diagnostic Full Output")
root.geometry("750x550")

frm = ttk.Frame(root, padding=10)
frm.pack(fill="both", expand=True)

ttk.Label(frm, text="JSON Input:").pack(anchor="w")

editor = tk.Text(frm, height=14, width=90)
editor.pack(fill="x")

editor.insert(
    tk.END,
    json.dumps(
        {
            "full_name": "Catalin George Festila",
            "city": "Falticeni",
            "birth_date": "1976-03-07",
            "nicknames": ["catafest", "mythcat"]
        },
        indent=2
    )
)

ttk.Button(frm, text="Run", command=process_json).pack(pady=10)

ttk.Label(frm, text="Output:").pack(anchor="w")

output = tk.Text(frm, height=14, width=90)
output.pack(fill="both", expand=True)

root.mainloop()