[Python cookbook learning notes] adds an entry to the dictionary

Given a dictionary D, direct d [Key] = value. If the key is not D, an entry is automatically added to D.

D = {'name': 'Small C '}
Print d
D ['age'] = 21
Print d

---------- Python ----------
{'Name': '\ xd0 \ xa1c '}
{'Age': 21, 'name': '\ xd0 \ xa1c '}

We can use the setdefault method of dict to do this. For example, we are creating a ing dictionary from words to pages to map each word to the page number of this page that appears.

Def addword (index, word, pagenum ):
Index. setdefault (word, []). append (pagenum)

Index. setdefault (word, []) returns a list, so you can call the append method.

Broadly speaking, D. setdefault (Key, value) returns Value

Several ways to create a dictionary

1, D = {'name': 'Small C', 'age': 21}

2, D = dict (name = "small C", age = 21)

3, D = dict ({'name': 'Small C'}, age = 21)