Splitting a semicolon-separated string to a dictionary, in Python

There's no builtin, but you can accomplish this fairly simply with a generator comprehension:

s= "Name1=Value1;Name2=Value2;Name3=Value3"
dict(item.split("=") for item in s.split(";"))

[Edit] From your update you indicate you may need to handle quoting. This does complicate things, depending on what the exact format you are looking for is (what quote chars are accepted, what escape chars etc). You may want to look at the csv module to see if it can cover your format. Here's an example: (Note that the API is a little clunky for this example, as CSV is designed to iterate through a sequence of records, hence the .next() calls I'm making to just look at the first line. Adjust to suit your needs):

>>> s = "Name1='Value=2';Name2=Value2;Name3=Value3"

>>> dict(csv.reader([item], delimiter='=', quotechar="'").next() 
         for item in csv.reader([s], delimiter=';', quotechar="'").next())

{'Name2': 'Value2', 'Name3': 'Value3', 'Name1': 'Value1=2'}

Depending on the exact structure of your format, you may need to write your own simple parser however.

s1 = "Name1=Value1;Name2=Value2;Name3=Value3"

dict(map(lambda x: x.split('='), s1.split(';')))

This comes close to doing what you wanted:

>>> import urlparse
>>> urlparse.parse_qs("Name1=Value1;Name2=Value2;Name3=Value3")
{'Name2': ['Value2'], 'Name3': ['Value3'], 'Name1': ['Value1']}