Python [3]-dictionary dic And set, python dictionary dicset

Python [3]-dictionary dic And set, python dictionary dicset
I. dictionary dict

Dict is stored as a key-value pair. The creation method is to use braces {} and separate the key and value with a colon.

>>> d={'chen':60,'zhang':80}>>> print d{'chen': 60, 'zhang': 80}

Assignment operation

>>> d['chen']=65>>> print d{'chen': 65, 'zhang': 80}

Value: get (). You can set the default value for the get () method.

>>> print d.get('liu',0)0

 

Delete: You can use pop to delete a value and return the deleted element.

d['liu']=85>>> d{'chen': 60, 'liu': 85, 'zhang': 80}>>> d.pop('liu')85>>> d{'chen': 60, 'zhang': 80}

The keys () and values () Methods return the dictionary's key and Value Sets respectively. Although there is no specific order for key-value pairs, the results returned by these two methods are in the same order.

>>> d.keys()['chen', 'zhang']>>> d.values()[60, 80]

Dictionary merge: You can use the update () method to merge two dictionaries.

>>> d1={'a':100,'b':99}>>> d.update(d1)>>> d{'chen': 60, 'a': 100, 'b': 99, 'zhang': 80}

 

Complete demo:

d={"chen":60,"zhang":80}print(d)d['chen']=65print(d)print(d.get("liu",0))d['liu']=85print(d)d.pop('liu')print(d)print(d.keys())print(d.values())d1={'a':100,'b':99}d.update(d1)print(d)

 

Ii. set

1. set is used to store a set of unique key values, but not their values.

2. set can be created in two ways:

• Use the set function. The parameter is a list set, for example, s = set ([1, 2, 3, 4, 5]);
• Set literal volume wrapped in braces, for example, s = {1, 3 }.

3. set common operations

• The add (key) method adds an element to the set. It does not take effect if the element already exists.
• The remove (key) method can delete elements.
• | Operators can take the Union of sets.
• & Operator returns the intersection of Sets
• -Calculate the difference between the two sets.
• ^ Returns the exclusive or of two sets.

>>> s=set([1,2,3,4,5])>>> print sset([1, 2, 3, 4, 5])>>> s.add(6)>>> print sset([1, 2, 3, 4, 5, 6])>>> s.add(6)>>> print sset([1, 2, 3, 4, 5, 6])>>> s.remove(6)>>> print sset([1, 2, 3, 4, 5])>>> s1=set([3,5,7])>>> print s&s1set([3, 5])>>> print s|s1set([1, 2, 3, 4, 5, 7])>>> print s1-sset([7])>>> print s^s1set([1, 2, 4, 7])

 

• Issubset (): determines whether a set is a subset of another set;
• Issuperset (): determines whether a set is a superset of another set.

>>> sset([1, 2, 3, 4, 5])>>> {1,3,5}.issubset(s)True>>> s.issuperset({1,5})True