Implementing-cryptography-using-python

Chapter 1 ■ Introduction to Cryptography and Python 19
>>> while (count < 5):
>>> print (count)
>>> count = count + 1
>>> else:
>>> print ("The count is greater than 5")
>>> print ("The loop has finished.")
Using Files
In this book, we will be using external files to both read and write. We will
be using the file function, which takes the file location and then performs an
operation. Table 1.9 shows the operations available.
Table 1.9: File Operations
OPERATOR
R
DESCRIPTION
Open text file for reading. The stream is positioned at the beginning of
the file.
r+ Open for reading and writing. The stream is positioned at the beginning
of the file.
W
Truncate file to zero length or create text file for writing. The stream is
positioned at the beginning of the file.
w+ Open for reading and writing. The file is created if it does not exist,
otherwise it is truncated. The stream is positioned at the beginning of the
file.
Append
Open for writing/appending to the file. The file is created if it does not
exist. The stream is positioned at the end of the file. Subsequent writes to
the file will always end up at the current end of file.
a+ Open for reading and writing. The file is created if it does not exist. The
stream is positioned at the end of the file. Subsequent writes to the file
will always end up at the current end of file.
An example we will be using later in this chapter is the following:
>>> # Python 2.7
>>> f=file('dictionary.txt', 'r')
>>> words = [word.strip() for word in f]
>>> f.close()
>>> # Python 3.5
>>> f = open('dictionary.txt', 'r')
>>> words = [word.strip() for word in f]
>>> f.close()