Python - Building a HTTP request string variable

Question

I am trying to build the HTTP request string in the variable "full_req". Here is how a HTTP request looks:

GET /images/logo/ HTTP/1.1
Host: www.google.com
Connection: close

I already wrote python code so if I enter a url, "http://www.google.com/images/logo/googlelogo.png", it will split the url into 3 parts. Below are the variables that I used:

host (contains www.google.com)
path (contains /images/logo/)
file (contains googlelogo.png)
port (Its showing None but I think its suppose to say 80)

How do I assign HTTP request string to full_req variable so if I print this variable, it contains all three lines?

print(full_req)

tried string concatenation but it didn't work. I used this resource: http://www.skymind.com/~ocrow/python_string/

what is your goal? if'youre just trying to make a request, you should better use urllib2/urllib or requests... — mata
– mata, Commented Apr 21, 2013 at 21:43

Martijn Pieters · Accepted Answer · 2013-04-21 23:09:54Z

4

You could use string formatting:

request = 'GET {path} HTTP 1.1\r\nHost: {host}\r\nConnection: Close\r\n\r\n'.format(path=path, host=host)

This uses the modern str.format() method, but you could use classic string operations as well.

edited Apr 21, 2013 at 23:09

answered Apr 21, 2013 at 21:51

Martijn Pieters

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Comments

diego nunes · Accepted Answer · 2013-04-28 22:55:07Z

3

. . String format or simple concatenation should do it.

. . There are many options and it depends on versions. In Python2 it is common to use % operator syntax, but in Python3 you mainly use the .format method on string objects.

. . You can still use the simplest form of concatenation with the + operator, with something like this:

full_req = 'GET ' + path + ' HTTP/1.1\r\n' \
           'HOST: ' + host + '\r\n' + \
           'Connection: close'

. . Note that it won't request the file (as per your example you are requesting the parent folder, not the file itself) and if you plan to download the file rather than just experiment with HTTP protocol, there are built-in modules to do that (check urllib.retrieve).

. . The port number (usually 80 for HTTP) would be used when opening the connection (in a socket), but your example doesn't seem to do that part of the request as well.

. Amplexos.

edited Apr 28, 2013 at 22:55

answered Apr 21, 2013 at 21:50

diego nunes

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3 Comments

Martijn Pieters Over a year ago

Note that string concatenation is more cumbersome than string formatting. Otherwise, good points.

Damon Over a year ago

I am actually trying to display an image on screen. Why do I need save a file?

Martijn Pieters Over a year ago

You don't have to save the file to disk; the named libraries can still help you achieve what you want.

Lucas Jones · Accepted Answer · 2013-04-21 21:51:37Z

2

Try:

def request(host, path, file):
    return '''GET %s%s HTTP/1.1\r
Host: %s\r
Connection: close''' % (path, file, host)

As far as I am aware, the port isn't included in the actual HTTP request. The key here is the use of the % string formatting operator.

answered Apr 21, 2013 at 21:51

Lucas Jones

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4 Comments

diego nunes Over a year ago

It is nice the clear out that your file can use the "\n"-only (linux style) line-breaks, but RFC2616 defines the "right" line break as "\r\n", so it's better to set the breaks manually.

Lucas Jones Over a year ago

@DiegoNunes: Thanks for the link, I actually had no idea! I'll modify the answer.

Damon Over a year ago

Its not storing the HTTP request in a variable tho

Lucas Jones Over a year ago

To store the result in a variable, use req = request(host, path, file) after you've defined the function. Alternatively, just write req = '''GET %s%s HTTP/1.1\r, etc.

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