The difference between list function and se function t in python

list literally means a set. In Python, the elements in the List are represented by square brackets []. You can define a List like this:

L = [12, 'China', 19.998]

In Python List is ordered, so if you want to access the List, you must obviously access it through the serial number, just like the subscript of the array, the subscript starts from 0:

>>> print L[0] 12

List can also be accessed in reverse order, through " The subscript "xth from last" represents the serial number. For example, the subscript -1 represents the first element from last:

>>> L = [12, 'China', 19.998] >>> print L[-1] 19.998

List is added to the end through the built-in append() method, and insert( ) method is added to the specified position (the subscript starts from 0):

>>> L = [12, 'China', 19.998] >>> L.append('Jack') >>> print L [12, 'China', 19.998, 'Jack'] >>> L.insert(1, 3.14) >>> print L [12, 3.14, 'China', 19.998, 'Jack'] >>>

2. Set is also a set of numbers, unordered, and the content cannot be repeated. It is created by calling the set() method:

>>> s = set(['A', 'B', 'C'])

The meaning of accessing a set is just to check whether an element is in the set. Pay attention to case sensitivity:

>>> print 'A' in s True>>> print 'D' in s False

Also traverse through for:

s = set([('Adam', 95), ('Lisa', 85), ('Bart', 59)]) for x in s: print x[0],':',x[1] >>> Lisa : 85 Adam : 95 Bart : 59

Through add and remove To add and delete elements (keep them non-repeating), when adding elements, use the add() method of set

>>> s = set([1, 2, 3]) >>> s.add(4) >>> print s set([1, 2, 3, 4])

If the added element already exists in the set, add() will not report an error, but it will not be added. In:

>>> s = set([1, 2, 3]) >>> s.add(3) >>> print s set([1, 2, 3])

When deleting elements in a set, use the set's remove() method:

>>> s = set([1, 2, 3, 4]) >>> s.remove(4) >>> print sset([1, 2, 3])

If the deleted element does not exist in the set, remove() will report an error:

>>> s = set([1, 2, 3]) >>> s.remove(4) Traceback (most recent call last): File "", line 1, in K eyError: 4

So if we want to determine whether an element meets some different conditions, using set is the best choice. The following example:

months = set(['Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec',]) x1 = 'Feb' x2 = 'Sun' if x1 in months: print 'x1: ok' else: print 'x1: error' if x2 in months: print 'x2: ok' else: print 'x2: error' >>> x1: ok x2: error

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