>>> ["foo", "bar", "baz"].index("bar")
1
Reference: Data Structures > More on Lists
Caveats follow
Note that while this is perhaps the cleanest way to answer the question as asked, index is a rather weak component of the list API, and I can't remember the last time I used it in anger. It's been pointed out to me in the comments that because this answer is heavily referenced, it should be made more complete. Some caveats about list.index follow. It is probably worth initially taking a look at the documentation for it:
list.index(x[, start[, end]])
Return zero-based index in the list of the first item whose value is equal to x. Raises a ValueError if there is no such item.
The optional arguments start and end are interpreted as in the slice notation and are used to limit the search to a particular subsequence of the list. The returned index is computed relative to the beginning of the full sequence rather than the start argument.
Linear time-complexity in list length
An index call checks every element of the list in order, until it finds a match. If your list is long, and you don't know roughly where in the list it occurs, this search could become a bottleneck. In that case, you should consider a different data structure. Note that if you know roughly where to find the match, you can give index a hint. For instance, in this snippet, l.index(999_999, 999_990, 1_000_000) is roughly five orders of magnitude faster than straight l.index(999_999), because the former only has to search 10 entries, while the latter searches a million:
>>> import timeit
>>> timeit.timeit('l.index(999_999)', setup='l = list(range(0, 1_000_000))', number=1000)
9.356267921015387
>>> timeit.timeit('l.index(999_999, 999_990, 1_000_000)', setup='l = list(range(0, 1_000_000))', number=1000)
0.0004404920036904514
Only returns the index of the first match to its argument
A call to index searches through the list in order until it finds a match, and stops there. If you expect to need indices of more matches, you should use a list comprehension, or generator expression.
>>> [1, 1].index(1)
0
>>> [i for i, e in enumerate([1, 2, 1]) if e == 1]
[0, 2]
>>> g = (i for i, e in enumerate([1, 2, 1]) if e == 1)
>>> next(g)
0
>>> next(g)
2
Most places where I once would have used index, I now use a list comprehension or generator expression because they're more generalizable. So if you're considering reaching for index, take a look at these excellent Python features.
Throws if element not present in list
A call to index results in a ValueError if the item's not present.
>>> [1, 1].index(2)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: 2 is not in list
If the item might not be present in the list, you should either
- Check for it first with
item in my_list (clean, readable approach), or
- Wrap the
index call in a try/except block which catches ValueError (probably faster, at least when the list to search is long, and the item is usually present.)
Best Answer
It might be a good idea to edit your question with exactly what you'd like to do with the information you read. However from what you've said so far:
The ID of the item being edited will already be passed through to the event receiver via SPItemEventProperties so there is no need to look it up. If you need to look up a different item in the list (or indeed in a different list altogether), the Accessing list items using the object model page on SharePoint Dev Wiki gives you all of the options. A good general rule is use SPQuery to get best performance on the whole.
Note: There is a pretty good page on the SharePoint Dev Wiki demonstrating how to write an event receiver. It shows how to query and obtain a list item title.
Update after comments:
Once you have an SPListItem object, you can find its GUID through the UniqueId property. In the "Accessing lists" wiki link I've provided above the code samples show how to use the Title property.
Every piece of data you need to access within SharePoint should be available through the object model. This is a simplification, but generally the pages themselves are rendered from template files on the server and combined with data in the database to display to the user. So editing the page programmatically or through its source isn't going to work.
Apologies if I'm making an incorrect assumption but you sound fairly new to SharePoint development. I strongly recommend you read at least the first few chapters of Inside Windows SharePoint Services 3.0 as the inner workings of SharePoint are important to get a good understanding of and this book should help a lot. There is a section of event receivers in it as well.