What is the role of python for writing dynamic web pages? Does it play an equivalent role to php?
If so, can it do all the same things as php (MySql, file manipulation, sending emails, ...)
Python's main (only?) limitation compared to PHP is its syntax.  Although in most situations it doesn't matter whether you're delimiting statements and blocks with semi-colons and braces (PHP) or line breaks and indentation (Python), this does become a bit of an issue when doing templating.  Templating typically requires inserting chunks of code at an indentation level dictated by the surrounding context rather than the embedded code itself.  This runs very much against the grain of Python syntax.
There have been some attempts made to create a useful mapping of Python into something that can be injected into templates, but it seems that there is inevitably some loss of expressiveness.  Whether the compromise is nonetheless still more powerful than PHP is another matter.
What is the role of python on the internet?