The Meaning and Usage of set in python

What does set mean in python?

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

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

The significance of accessing an set is simply to see if an element is in the collection, paying attention to case sensitivity:

>>> print 'A' in sTrue>>> print 'D' in sFalse

It is also traversed through for:

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

Use add and remove to add and delete elements (without duplication). When adding elements, use add () method of set

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

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

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

When deleting an element in set, use the remove () method of set:

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

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

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

So if we want to judge whether an element meets a number of different conditions, set is the best choice, as shown in 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: okx2: error

In addition, the computational efficiency of set is higher than that of list.

The above is about SET in PY usage and related knowledge points, thank you for reading and support of this site.