Chapter 13, Building Graphical User Interfaces

1. Graphical User Interface, which allows a user to interact with electronic devices.
2. A constructor is a special type of method (function) that is used to initialize the instance members of the class. Implementation of the__init__ method. A destructor is a special method called automatically during the destruction of an object. Implementation of the__del__ method.
3. Self is an object reference to the object itself; therefore, they are the same.
4. Tkinter is a Python binding to the Tk GUI toolkit. It is the standard Python interface to the Tk GUI toolkit, and is Python's de facto standard GUI. Tkinter is included with standard Linux, Microsoft Windows, and macOS X installs of Python. The name Tkinter comes from the Tk interface. PyQt is a Python binding of the cross-platform GUI toolkit Qt, implemented as a Python plugin. PyQt is free software developed by the British firm Riverbank Computing. wxPython is a wrapper for the cross-platform GUI API wxWidgets for the Python programming language. It is one of the alternatives to Tkinter, which is bundled with Python. It is implemented as a Python extension module. Other popular alternatives are PyGTK, its successor PyGObject, and PyQt.
5. Following is the answer:

def copy(source, destination):
    with open(source, "w") as fw, open(destination,"r") as fr:
        fw.writelines(fr)
copy(source_file_name1, file_name2)

6. Following is the answer:

fname = input("Enter file name: ")
l=input("Enter letter to be searched:")
k = 0
with open(fname, 'r') as f:
    for line in f:
        words = line.split()
        for i in words:
            for letter in i:
                if(letter==l):
                    k=k+1
print("Occurrences of the letter:")
print(k)