11.7 11.8 With Statements and Web Fetching¶

The with method automatically closes the file when finished, which is good, cause people forget
Context Manager
Automates the process of doing common operations at the start of some tasks, as well as automating some operations at the end of some tasks.

The Python with statement makes using context managers easy. The general form of a with statement is:

with <create some object that understands context> as <some name>:
    do some stuff with the object
    ...

When the program exits the with block, the context manager handles the common stuff that normally happens. For example closing a file.

Example¶

mydata.txt
1 2 3
4 5 6

with open('mydata.txt') as md:
    print(md)
    for line in md:
        print(line)
print(md)

<openfile 'mydata.txt', mode 'r'>
1 2 3

4 5 6

<closedfile 'mydata.txt', mode 'r'>

11.8 Fetching Something From The Web¶

We’ll need permission to write to the destination filename, and the file will be created in the “current directory” - i.e. the same folder that the Python program is saved in.
If we are behind a proxy server that requires authentication, (as some students are), this may require some more special handling to work around our proxy. Use a local resource for the purpose of this demonstration!

We will try to retrieve the content of the HTML of this page as in the following code.

import urllib.request

def retrieve_page(url):
    """ Retrieve the contents of a web page.
    """
    my_socket = urllib.request.urlopen(url)
    dta = my_socket.read()
    return dta

the_text = retrieve_page("https://runestone.academy/runestone/books/published/thinkcspy/Files/FetchingSomethingFromTheWeb.html")
print(the_text)