Form with Name & Age Validation | Python Tkinter GUI 🐍

Описание: Create a simple form in Python Tkinter with input validation! 🐍
This GUI takes a Full Name (alphabets only) and Age (numbers only), then displays the entered data with a Submit button.

🔎 Code Logic (Quick Explanation):
Entry with validatecommand → restricts input in real-time
Name field → accepts only alphabets
Age field → accepts only digits
Submit button → shows entered details using a popup
validate_name → allows only alphabets (isalpha() check).
validate_age → allows only digits (isdigit() check).
validate="key" + validatecommand → restricts input as user types.
messagebox.showinfo() → displays submitted values.

By default, an Entry widget accepts any input (letters, numbers, symbols).
If we want to restrict input while typing, we need to attach a validation function.

Tkinter’s validatecommand option does this — but it expects a string reference to a Tcl function, not a direct Python function.
That’s where root.register() comes in. ✅

🟢 What root.register() Does
root.register(python_function)
→ Converts your Python function into a Tkinter-compatible Tcl function.
Then Tkinter can call this function whenever the user types something in the Entry box.

root.register(validate_name)
→ Wraps the validate_name Python function so Tkinter can use it internally.

"%P"
→ Special substitution code that passes the new value of the Entry box to the function each time the user types.

validate="key"
→ Ensures validation happens as the user presses keys (not after they press Enter).

So when you type into the Name box:
Tkinter calls validate_name(new_value) automatically.
If the function returns True, the new character is accepted.
If False, the keystroke is ignored.

A beginner-friendly Python GUI project to understand validation in Tkinter forms. 🚀

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