Transcript Recitation 11 - Tel Aviv University

Programming for Engineers in Python
Recitation 11
Plan
 GUI
 Swampy
 Text widgets
 PyPad
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Install Swampy
 Download Swampy:
 http://greenteapress.com/thinkpython/swampy/swampy



3
2.0.python2.zip
Unzip to C:\Python27\Lib\site-packages
Now you should have a directory C:\Python27\Lib\sitepackages\swampy-2.0
Download this file http://db.tt/gQqPvRok (it might open as a
text file, right click and choose ‘Save as…’) and also put it in
C:\Python27\Lib\site-packages, making sure its name is
swampy.pth
Now you should have a file C:\Python27\Lib\sitepackages\swampy.pth
Check Swampy was installed
 Open the shell (IDLE)
 Run the following commands to check that Swampy is
working:
>>> import Tkinter
>>> from Gui import *
>>> g=Gui()
>>> g.mainloop()
 If you see a window like this ->
then the installation worked
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GUI - reminder
 Graphical User Interface
 The part of the program that communicates with the human
user
 Computer → Human: graphics (sometimes audio & even
vibrations)
 Human → Computer: keyboard & mouse (sometimes even
touchscreen & microphone)
 In many applications this is the most important part of the
program
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History of GUI
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http://www.youtube.com/watch?v=TZGGUrom1Mg
Widgets
 In class:
 Button
 Label
 Canvas
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More widgets!
 Textual input widgets:
 Entry – single line
entry_example.py: https://gist.github.com/1523427
 Text – multiple lines
text_example.py: https://gist.github.com/1523471
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Think Python 19.5
More complex example
 Change the color of a circle based on the color name given by
the user
circle_demo.py: thinkpython.com/code/circle_demo.py
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Think Python 19.5 pg. 185
PyNote – a Python Notepad
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Packing
>>> g = Gui()
>>> g.title('PyNote 0.1')
Creates the GUI & title
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Packing
>>>
g.col(weights=[1,0])
Creates a column that
holds widgets
Weights – later…
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Packing
>>> g.st(…)
st:
Scrollable text widget
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Packing
>>> g.row(weights=[1,0,0,0])
Creates a row that holds widgets
 The weights option determines which widget is resized and by
how much when the window is resized
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Resizing
 With weights=[1,0,0,0]
 Without specifying weights
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Packing
filename = g.en(text='filename.txt', width=16)
g.bu(text='...', command=browse)
g.bu(text='Save', command=save)
g.bu(text='Load', command=load)
g.bu(text='New', command=new)
g.bu(text='Quit', command=quit_)
g.bu: button widget
g.en: entry widget (one line of text)
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Check if a file exists
 os.path.exists(filename)
 Returns True if file exists, False if it does not
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Command
g.bu(text='Save', command=save)
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def save():
'''Saves the current note in a file'''
if exists(filename.get()): # exists is os.path.exists
if not tkMessageBox.askyesno ('Save','File already
exists, do you want to overwrite?'):
return
f = open(filename.get(),'w')
f.write(textbox.text.get(0.0, END))
f.close()
tkMessageBox.showinfo('Save','File saved: ‘
+filename.get())
Event driven programming
 Nothing happens until the user initiates an event
 When the user clicks the button the command is called
 Now the GUI is “frozen” until the command returns
 When it returns, the GUI is released
>>> def freeze():
time.sleep(5)
>>> g=Gui()
>>> g.bu(text=‘Freeze!’,command=freeze)
>>> g.mainloop()
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http://www.tutorialspoint.com/python/tk_messagebox.htm
tkMessageBox
 Creates a message box that asks the user a question or gives
him information
 Usually with a button or two
 Examples:
tkMessageBox.showinfo('Load','File does
not exist: '+filename.get())
tkMessageBox.askyesno('Save','File already exists, do you want to
overwrite?')
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tkMessageBox.askyesno('Quit?','Do you want to quit?')
tkMessageBox.askyesno('Save','File already exists, do you want to
overwrite?')
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tkMessageBox.askyesno('Quit?','Do you want to quit?')
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tkMessageBox.showinfo('Load','File does not exist: ‘ +
filename.get())
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Load command
def load():
'''Opens a file to the text widget'''
if not exists(filename.get()):
tkMessageBox.showinfo('Load','File does not exist: '
+filename.get())
return
new() # delete previous note from text widget
f = open(filename.get())
t = f.read()
textbox.text.insert(0.0, t)
f.close()
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File dialog box
 We can get the file by writing/copy-pasting its name, but it’s
easier with a file dialog box:
t = tkFileDialog.askopenfilename()
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File dialog box – contd.
 We use the dialog box in the browse function which is called
by the ‘…’ button
def browse():
'''opens a file dialog and sets its result to the
filename entry'''
t = tkFileDialog.askopenfilename()
if t:
filename.delete(0,END)
filename.insert(0,t)
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Exit the GUI
 User:
 By clicking the windows X icon
 By pressing Ctrl-C in the shell
 Program:
 By calling g.destroy()
 Example – quit_() function (‘_’ is used in the name because quit is a
python word):
def quit_():
'''asks the user if he wants to quit'''
if tkMessageBox.askyesno ('Quit?','Do you want to
quit?'):
g.destroy() # this actually quits the GUI
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Reverse text
 We create a button that will reverse all the words in the text
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Reverse text
 We create a button that will reverse all the words in the text
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Reverse word
def reverse_word(word):
return word[-1::-1].capitalize()
 We used capitalize so that the words will look nice:
January -> Yraunaj and not yraunaJ
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Reverse text
def reverse():
orig = textbox.text.get(0.0, END)
new() # delete the current text
for line in orig.split('\n'):
for word in line.split(' '):
textbox.text.insert(END, reverse_word(word))
textbox.text.insert(END, ' ') # ‘ ‘ is a space
textbox.text.insert(END, '\n') # newline
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Reverse button
g.bu(text='Reverse', command=reverse)
 Add functionality, then add a button
 We can now add other functionalities (if time permits):
 Count words
 Count characters (frequency counter)
 Count lines
 Decipher (HW 5)
 Markov analysis (HW 4)
 Translate (http://www.catonmat.net/blog/python-library-for-
google-translate/)
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