# copy_file.py
#
# Copy the contents of the source file to the desination file.
#

from sys import argv

def copy_file(from_file_name, to_file_name):
    """
    Copy the contents of the source file named from_file_name
    to the desination file named to_file_name. Create the 
    destination file if it doesn't already exist. Overwrite the 
    current contents of an existing destination file.
    """
    from_file = open(from_file_name, mode='r')
    to_file   = open(to_file_name,   mode='w')
    
    contents = from_file.read()
    to_file.write(contents)

if __name__ == '__main__':
    if len(argv) != 3:
        print('Usage: ipython copy_file.py source_file_name target_file_name')
    else:
        copy_file(argv[1], argv[2])