Sending XML Data Over HTTP

Readable XML Payloads

XML is structured across multiple lines, with nested elements often separated by indentation. Representing that structure in an ordinary Python string can be awkward because line breaks must be written with escape sequences such as \n. Triple-quoted strings provide a more readable way to represent XML in Python before preparing it as a payload to send across the web.

Quote Boundaries

A triple-quoted string begins with three consecutive single quotes or three consecutive double quotes and ends with a matching set of three quotes. Everything between those boundaries belongs to the string value. Because the opening and closing quotes can surround several lines, the string can contain line breaks, indentation, and spaces directly.

xml_data = '''<message>
    <text>Hello</text>
</message>'''

Two Equivalent Styles

xml_single = '''<user>
    <name>Ada</name>
</user>'''

xml_double = """<user>
    <name>Ada</name>
</user>"""

Formatting Becomes Content

Triple-quoted strings preserve the formatting typed between the delimiters. Pressing Enter in the source code adds a newline character to the string. Adding spaces for indentation adds those spaces to the string as well. This means the visual layout of the triple-quoted portion is not merely decoration: it directly contributes to the resulting string value.

From XML Text to Payload

A triple-quoted string does not perform the web transfer by itself. Its role is to make the XML data readable and preserve its structure while the data is represented in Python. Once the XML has been stored as a string, that string can be used as a payload prepared for sending across the web.

Mistakes with Layout

• Assuming indentation is ignored

  The spaces before the text element are inside the triple-quoted boundaries, so they become part of the string value.

  Fix: Treat every space and line break between the opening and closing triple quotes as content.

• Expecting triple quotes to send the XML automatically

  Triple quotes create a multi-line string; they do not themselves perform the web transfer.

  Fix: Use the resulting string as XML data when preparing a payload to send across the web.

• Thinking triple single quotes and triple double quotes have different multi-line behavior

  Both quote styles create multi-line strings and preserve the content between their delimiters.

  Fix: Choose the style that is more convenient or consistent with the surrounding code.

• Treating code indentation outside the string as automatically part of the value

  The important boundary is what appears between the opening and closing triple quotes. Spaces outside those boundaries are not part of the string content.

  Fix: Inspect the text inside the delimiters when deciding which spaces and line breaks belong to the XML string.

Practice the Mapping

Key Takeaways

1. Triple single quotes and triple double quotes both create multi-line Python strings.
2. Everything between the opening and closing triple quotes, including line breaks, indentation, and spaces, becomes part of the string value.
3. Triple-quoted strings make XML easier to read because the XML structure can be written directly across multiple lines.
4. The choice between triple single quotes and triple double quotes is a style and convenience decision.
5. The resulting string represents the XML data; it can then be prepared as a payload to send across the web.