3. Feet to meters
from tkinter import *
from tkinter import ttk
def calculate(feet):
"""
Convert feet to meters.
Parameters:
feet (str): The number of feet to convert to meters.
Returns:
float: The equivalent number of meters rounded to 2 decimal places.
"""
try:
feet = float(feet)
return round(0.3048 * feet, 2)
except ValueError:
pass
def set_meters():
"""
Set the meters StringVar with the calculated meters from the feet StringVar.
Then set the focus back to the feet_entry field.
"""
meters.set(calculate(feet.get()))
feet_entry.focus()
# Create the main window
root = Tk()
root.title("Feet to Meters")
# Create the main frame
mainframe = ttk.Frame(root, padding="3 3 12 12")
mainframe.grid(column=0, row=0, sticky=(N, W, E, S))
root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=1)
# Create the feet StringVar and entry field
feet = StringVar()
feet_entry = ttk.Entry(mainframe, width=7, textvariable=feet)
feet_entry.grid(column=2, row=1, sticky=(W, E))
# Create the meters StringVar and label
meters = StringVar()
ttk.Label(mainframe, textvariable=meters).grid(column=2, row=2, sticky=(W, E))
# Create the calculate button
ttk.Button(mainframe, text="Calculate", command=set_meters).grid(
column=3, row=3, sticky=W
)
# Create the labels
ttk.Label(mainframe, text="feet").grid(column=3, row=1, sticky=W)
ttk.Label(mainframe, text="is equivalent to").grid(column=1, row=2, sticky=E)
ttk.Label(mainframe, text="meters").grid(column=3, row=2, sticky=W)
# Configure the padding for all child widgets of mainframe
for child in mainframe.winfo_children():
child.grid_configure(padx=5, pady=5)
# Set the initial focus to the feet_entry field
feet_entry.focus()
# Bind the return key to the set_meters function
root.bind("<Return>", lambda _: set_meters())
# Start the main event loop
root.mainloop()
3.1. Code walk through
from tkinter import *
from tkinter import ttk
These lines import all the necessary modules from tkinter and ttk (themed tkinter) for creating a GUI application.
def calculate(value):
"""
Convert feet to meters.
Parameters:
value (str): The number of feet to convert to meters.
Returns:
float: The equivalent number of meters rounded to 2 decimal places.
"""
try:
value = float(value)
return round(0.3048 * value, 2)
except ValueError:
pass
def set_meters():
"""
Set the meters StringVar with the calculated meters from the feet StringVar.
Then set the focus back to the feet_entry field.
"""
meters.set(calculate(feet.get()))
feet_entry.focus()
This function is used to convert feet to meters. It tries to get the value from the feet variable, convert it to meters, and set the meters variable to the result. If the value cannot be converted to a float, it does nothing.
root = Tk()
root.title("Feet to Meters")
This creates the main window (root) of the application and sets its title.
mainframe = ttk.Frame(root, padding="3 3 12 12")
mainframe.grid(column=0, row=0, sticky=(N, W, E, S))
root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=1)
This creates a frame widget, which will hold all other widgets. It is placed in the root window and configured to expand as the window is resized. The sticky parameter specifies how the frame should expand to fill the space allocated to it. In this case, the frame will expand to fill the entire space in the North, West, East, and South directions. The next two lines configure the root window to expand in both the x and y directions by setting the weight of the column and row to 1. This ensures that the mainframe object will fill the entire window.
feet = StringVar()
feet_entry = ttk.Entry(mainframe, width=7, textvariable=feet)
feet_entry.grid(column=2, row=1, sticky=(W, E))
This creates a StringVar to hold the value of feet and an entry widget for the user to input the value. The entry widget is placed in the second column and first row of the grid.
StringVar() is a class in the tkinter module that holds a string data and provides helper functions for manipulating the values of widgets like Label and Entry. It works differently from normal Python variables and requires an interpreter that is created when an instance of Tk is made. StringVar can be created using a constructor that accepts a container widget, a value, and a name as optional arguments. StringVar is useful for creating and accessing variables in a graphical user interface ¹².
meters = StringVar()
ttk.Label(mainframe, textvariable=meters).grid(column=2, row=2, sticky=(W, E))
This creates another StringVar to hold the value of meters and a label widget to display it. The label widget is placed in the second column and second row of the grid.
ttk.Button(mainframe, text="Calculate", command=calculate).grid(column=3, row=3, sticky=W)
This creates a button widget that calls the calculate function when clicked.
ttk.Label(mainframe, text="feet").grid(column=3, row=1, sticky=W)
ttk.Label(mainframe, text="is equivalent to").grid(column=1, row=2, sticky=E)
ttk.Label(mainframe, text="meters").grid(column=3, row=2, sticky=W)
These lines create label widgets for the text “feet”, “is equivalent to”, and “meters”, and place them in the grid.
for child in mainframe.winfo_children():
child.grid_configure(padx=5, pady=5)
This loop adds padding to all widgets in the mainframe.
feet_entry.focus()
root.bind("<Return>", calculate)
This sets the focus to the feet_entry widget (so the user can start typing immediately) and binds the Return key to the calculate function.
root.mainloop()
Finally, this starts the event loop for the application, which waits for user actions.