Implementing-cryptography-using-python

28 Chapter 1 ■ Introduction to Cryptography and Python
>>> url = 'https://raw.githubusercontent.com/noidentity29/
AppliedCryptoPython/master/dictionary.txt'
>>> r = requests.get(url)
>>> with open('/Users/ShannonBray/Downloads/dictionary.txt', 'wb') as f:
>>> f.write(r.content)
>>>
>>> # Retrieve HTTP meta-data
>>> print(r.status_code)
>>> print(r.headers['content-type'])
>>> print(r.encoding)
In this script, the open method is used once again to write binary data to
a local file. If you execute the script and go to your Downloads directory, you
should see your newly downloaded text file named secrets.txt.
Utilizing the requests module, you can also easily retrieve relevant metadata
about your request, including the status code, headers, and much more. In the
preceding script, you can see how we access some of this metadata.
You can also elect to use the curl bash command, such as in the following
example:
curl -O https://raw.githubusercontent.com/noidentity29/AppliedCryptoPython/
master/secret.txt
curl -O https://raw.githubusercontent.com/noidentity29/AppliedCryptoPython/
master/dictionary.txt
Introducing Python Modules
Python modules are special packages that extend the language. You saw your
first module when you used the import math call shown previously. You can
examine the modules that are loaded by typing dir(). As shown with the math
module, when a module is preinstalled, we can use the import command to
upload it. To examine the modules that are preinstalled on your system, type
the following:
>>> help()
help> modules
help> modules hashlib
q
The hashlib is a built-in module that is preinstalled that will allow you to
run hash functions. We will discuss hashing in detail throughout this book, but
for now, we will explore the use of hashlib as a module. Type import hashlib,
then in the terminal type hashlib. (enter the dot after hashlib), and press the
Tab key. You should see a list of methods, as shown in Figure 1.4. You can explore
these methods by typing the module and method followed by a question mark,
such as hashlib.sha256?.