List is one of the most powerful structures in Python. It is defined as "a container that holds a number of other objects, in a given order". So it is quite general and extendable.
For List type, there are several aspects we need to know:
1. Generation
1.1. Direct way
a = []; b = [1,2,3]; c = ['today', 'is', 1, 'of', 'the', 0.5, 'day'];
b = list(1,2,3);
1.2. Sequence generation
a = [x**2 for x in range(10)]
1.3 Convert from other data structures
a = (1,2,3); b = list(a)
2. Access
2.1. Direct way
a = range(10); b = a[1:5]
2.2 Sequence way
a = range(100); b = [1,2,3,10,40]; c = [a[i] for i in b];
3. Modification (list-level)
3.1 list.
append() --- add item to the list
a.append(10);
3.2 list.
extend() --- add elements from list to the list
a.extend([1,2,3]);
3.3 list.
insert(i, x) --- add item to the list on specific location
a.insert(len(a), 10) is equivalent to a.append(10)
3.4 list.
remove(x) --- remove the first item from the list whose value is x, return error if there is no such item.
3.5 list.
pop([i]) --- Remove the item at the given position in the list, and return it. If no index is specified, a.pop() removes and returns the last item in the list.
3.6 list.
index(x) --- Return the index in the list of the
first item whose value is x, return error if there is no such item
3.7 list.
count(x) --- Return the number of times x appears in the list, return error if there is no such item
3.8 list.
sort() or list.sort(reverse = True) or list.reverse() --- sort the list ...
3.9
del statement --- delete either any element (del(a[0])) or the whole list! (del a). Powerful, yet dangerous :)
4. Nested List
If one generate a nested list as this:
a = [[a,b] for a in range(10) for b in range(5)]
To access to each individual:
a[i][j]
Some additional useful functions on List:
1. How to merge two lists?
c = a + b very straight forward, remember there is no a - b operation
NOTE: List is different from the matrix or vector as in Matlab, one can not directly run any mathematical operation on it, such as a = a + 1.
NOTE: two derived structures: Queue and Stack, how to do this? following examples:
1. Queue
a = range(10); a.append('new-entry'); a.pop(0);
2. Stack
a = range(10); a.append('new-entry'); a.pop();
