What does set mean in python

What does set mean in python?

set is a set of numbers, unordered, and the content cannot be Repeat, created by calling the set() method:

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

The meaning of accessing a set is only 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 passes for to traverse:

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

Add and delete elements through add and remove (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 set, add() will not report an error, but it will not be added:

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

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

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

If deleted If the 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 "<stdin>", line 1, in <module>
KeyError: 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

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

Related recommendations: "Python Tutorial"

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