Then the loop variable can use the singular form "url" - confirming as you type that the loop variable and what's in the collection match up. Style: it's a nice pattern to name the list variable with the letter "s" like "urls". It's very easy to "foreach" loop over all the elements in a list, seeing each element once. Omitting both start and end indexes yields a copy of the whole list - lst Foreach loop - for elem in list The original list is not modified, this creates a new list populated with elements from the original. Slices work to pull out parts of list just as with strings. (mentioned for completeness, I don't think we will ever need this function in CS106A.) You could use this to loop over a list and also modify it - loop over a copy, modify the original. Append() is simpler since it just goes on the end without any shifting and you don't have to think about index numbers. Lst.insert(index, x) - insert the element x so it is at the given index, shifting elements towards the end of the list as needed. Min(lst) max(lst) - Return the smallest or largest element in lst. > 'x' in lst # Therefore, check before calling. In other words, there is nothing as simple as str.find() for lists which IMHO seems ![]() Therefore check with in first, and only if x is in there call index(). Raises an error if x is not in there - this is rather inconvenient. Lst.index(x) - Look for first instance of x in lst and return its index. The + operation is an alternative to extend(), combining lists to make a bigger list (very analogous to + with strings) > # all elements of x are added at end, so lst is > # x is added as an *element* so lst is ] Lst.extend(lst2) - add all the elements of lst2 on to the end of lst. ValueError: list.remove(x): x not in list Note that pop() uses index numbers, but remove() uses the value, e.g. It's an error to remove() an elem not in the list - could use in to check first. Lst.remove( elem) - search the list for the first instance of elem and remove it. Raises an error if the index is not valid. lst.pop(0) removes the element at index 0. Lst.pop( index) - alternate version with the index to remove is given, e.g. Mnemonic: the exact opposite of append(). Lst.pop() - remove the element from the end of the list and return it, decreasing the length of the list by 1. Lst.append(x) - add x to the end of lst, increasing its length by 1. X in lst - boolean test if x is in lst (just like for string) Lst - access individual elements with square bracketsįor x in lst: - loop over contents, do not modify lst during loop ![]() As a convenience, it's allowable to have an extra comma at the end of the series of elements like this: Here is what that list looks like in memory The list is written within square brackets, and the elements are separated by commas. ![]() Here is the code to create a list of the three strings 'a' 'b' and 'c'. As elements are added and removed, Python maintains the elements as contiguous block alwayx indexed by the numbers 0.length-1 inclusive. Using the standard indexing scheme, the first element is at index 0, the next at index 1, and so on up to index length-1. Unlike strings, lists are "mutable" - they can be changed. The things inside a list are generically called "elements". Python Dictionaries Access Items Change Items Add Items Remove Items Loop Dictionaries Copy Dictionaries Nested Dictionaries Dictionary Methods Dictionary Exercise Python If.Else Python While Loops Python For Loops Python Functions Python Lambda Python Arrays Python Classes/Objects Python Inheritance Python Iterators Python Scope Python Modules Python Dates Python Math Python JSON Python RegEx Python PIP Python Try.A list contains series of any data type: strings, ints, other lists.
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