Programming Python (75 page)

"add a label on the top and form resizing"
from tkinter import *
colors = ['red',  'white',  'blue']
def gridbox(root):
Label(root, text='Grid').grid(columnspan=2)
row = 1
for color in colors:
lab = Label(root, text=color, relief=RIDGE,  width=25)
ent = Entry(root, bg=color,   relief=SUNKEN, width=50)
lab.grid(row=row, column=0, sticky=NSEW)
ent.grid(row=row, column=1, sticky=NSEW)
root.rowconfigure(row, weight=1)
row += 1
root.columnconfigure(0, weight=1)
root.columnconfigure(1, weight=1)
def packbox(root):
Label(root, text='Pack').pack()
for color in colors:
row = Frame(root)
lab = Label(row, text=color, relief=RIDGE,  width=25)
ent = Entry(row, bg=color,   relief=SUNKEN, width=50)
row.pack(side=TOP,   expand=YES, fill=BOTH)
lab.pack(side=LEFT,  expand=YES, fill=BOTH)
ent.pack(side=RIGHT, expand=YES, fill=BOTH)
root = Tk()
gridbox(Toplevel(root))
packbox(Toplevel(root))
Button(root, text='Quit', command=root.quit).pack()
mainloop()

Figure 9-32. grid and pack windows before resizing

Figure 9-33. grid and pack windows resized

Heavy rows and columns

With
pack
, we make each
row expandable by making the corresponding
Frame
expandable, with
expand=YES
and
fill=BOTH
. Gridders must be a bit more
specific: to get full expandability, call the grid container’s
rowconfigure
method for each
row and its
columnconfigure
for each column. To both methods, pass a weight option with a
value greater than zero to enable rows and columns to expand.
Weight defaults to zero (which means no expansion), and the grid
container in this script is just the top-level window. Using
different weights for different rows and columns makes them grow
at proportionally different rates.

Sticky widgets

With
pack
, we use
fill
options to stretch
widgets to fill their allocated space horizontally or
vertically, and
anchor
options to position widgets within their allocated space. With
grid
, the
sticky
option serves the roles of both
fill
and
anchor
in the packer. Gridded widgets
can optionally be made sticky on one side of their allocated
cell space (such as
anchor
)
or on more than one side to make them stretch (such as
fill
). Widgets can be made sticky in
four directions—
N
,
S
,
E
, and
W
, and concatenations of these letters
specify multiple-side stickiness. For instance, a sticky setting
of
W
left justifies the
widget in its allocated space (such as a packer
anchor=W
), and
NS
stretches the widget vertically
within its allocated space (such as a packer
fill=Y
).

Widget stickiness hasn’t been useful in examples thus far
because the layouts were regularly sized (widgets were no
smaller than their allocated grid cell space), and resizes
weren’t supported at all. Here, though,
Example 9-22
specifies
NSEW
stickiness to make
widgets stretch in all directions with their allocated
cells.

For more on input form layout, stay tuned for the form builder
utilities we’ll code near the end of
Chapter 12
and use again in
Chapter 13
, when developing a file transfer
and FTP client user interface. As we’ll see, doing forms well once
allows us to skip the details later. We’ll also use more custom form
layout code in the PyEdit program’s change dialog in
Chapter 11
, and the PyMailGUI example’s
email header fields in
Chapter 14
.

# simple 2D table, in default Tk root window
from tkinter import *
for i in range(5):
for j in range(4):
lab = Label(text='%d.%d' % (i, j), relief=RIDGE)
lab.grid(row=i, column=j, sticky=NSEW)
mainloop()

Figure 9-34. A 5 × 4 array of coordinate labels

# 2D table of input fields, default Tk root window
from tkinter import *
rows = []
for i in range(5):
cols = []
for j in range(4):
ent = Entry(relief=RIDGE)
ent.grid(row=i, column=j, sticky=NSEW)
ent.insert(END, '%d.%d' % (i, j))
cols.append(ent)
rows.append(cols)
def onPress():
for row in rows:
for col in row:
print(col.get(), end=' ')
print()
Button(text='Fetch', command=onPress).grid()
mainloop()

# add column sums, clearing
from tkinter import *
numrow, numcol = 5, 4
rows = []
for i in range(numrow):
cols = []
for j in range(numcol):
ent = Entry(relief=RIDGE)
ent.grid(row=i, column=j, sticky=NSEW)
ent.insert(END, '%d.%d' % (i, j))
cols.append(ent)
rows.append(cols)
sums = []
for i in range(numcol):
lab = Label(text='?', relief=SUNKEN)
lab.grid(row=numrow, column=i, sticky=NSEW)
sums.append(lab)
def onPrint():
for row in rows:
for col in row:
print(col.get(), end=' ')
print()
print()
def onSum():
tots = [0] * numcol
for i in range(numcol):
for j in range(numrow):
tots[i] += eval(rows[j][i].get())        # sum column
for i in range(numcol):
sums[i].config(text=str(tots[i]))            # display in GUI
def onClear():
for row in rows:
for col in row:
col.delete('0', END)
col.insert(END, '0.0')
for sum in sums:
sum.config(text='?')
import sys
Button(text='Sum',   command=onSum).grid(row=numrow+1, column=0)
Button(text='Print', command=onPrint).grid(row=numrow+1, column=1)
Button(text='Clear', command=onClear).grid(row=numrow+1, column=2)
Button(text='Quit',  command=sys.exit).grid(row=numrow+1, column=3)
mainloop()

Figure 9-36. Adding column sums

# recode as an embeddable class
from tkinter import *
from tkinter.filedialog import askopenfilename
from PP4E.Gui.Tour.quitter import Quitter          # reuse, pack, and grid
class SumGrid(Frame):
def __init__(self, parent=None, numrow=5, numcol=5):
Frame.__init__(self, parent)
self.numrow = numrow                       # I am a frame container
self.numcol = numcol                       # caller packs or grids me
self.makeWidgets(numrow, numcol)           # else only usable one way
def makeWidgets(self, numrow, numcol):
self.rows = []
for i in range(numrow):
cols = []
for j in range(numcol):
ent = Entry(self, relief=RIDGE)
ent.grid(row=i+1, column=j, sticky=NSEW)
ent.insert(END, '%d.%d' % (i, j))
cols.append(ent)
self.rows.append(cols)
self.sums = []
for i in range(numcol):
lab = Label(self, text='?', relief=SUNKEN)
lab.grid(row=numrow+1, column=i, sticky=NSEW)
self.sums.append(lab)
Button(self, text='Sum',   command=self.onSum).grid(row=0, column=0)
Button(self, text='Print', command=self.onPrint).grid(row=0, column=1)
Button(self, text='Clear', command=self.onClear).grid(row=0, column=2)
Button(self, text='Load',  command=self.onLoad).grid(row=0, column=3)
Quitter(self).grid(row=0, column=4)    # fails: Quitter(self).pack()
def onPrint(self):
for row in self.rows:
for col in row:
print(col.get(), end=' ')
print()
print()
def onSum(self):
tots = [0] * self.numcol
for i in range(self.numcol):
for j in range(self.numrow):
tots[i] += eval(self.rows[j][i].get())        # sum current data
for i in range(self.numcol):
self.sums[i].config(text=str(tots[i]))
def onClear(self):
for row in self.rows:
for col in row:
col.delete('0', END)                          # delete content
col.insert(END, '0.0')                        # preserve display
for sum in self.sums:
sum.config(text='?')
def onLoad(self):
file = askopenfilename()
if file:
for row in self.rows:
for col in row: col.grid_forget()             # erase current gui
for sum in self.sums:
sum.grid_forget()
filelines   = open(file, 'r').readlines()         # load file data
self.numrow = len(filelines)                      # resize to data
self.numcol = len(filelines[0].split())
self.makeWidgets(self.numrow, self.numcol)
for (row, line) in enumerate(filelines):          # load into gui
fields = line.split()
for col in range(self.numcol):
self.rows[row][col].delete('0', END)
self.rows[row][col].insert(END, fields[col])
if __name__ == '__main__':
import sys
root = Tk()
root.title('Summer Grid')
if len(sys.argv) != 3:
SumGrid(root).pack()    # .grid() works here too
else:
rows, cols = eval(sys.argv[1]), eval(sys.argv[2])
SumGrid(root, rows, cols).pack()
mainloop()