Lists and dictionaries in Python (ii)

three. Dictionaries and related uses

1. Dictionary definition dict{}

2. Dictionary features: Dictionary is unordered, key-value key value pair form, key value is not duplicated

3. Assignment of dictionaries: dicta = {Keya:valuea, Keyb:valueb, KEYC:VALUEC}

4. Dictionary value: Dicta[keya] Dicta.get (Keya)

5. All keys of the Dictionary: Dicta.keys () Key-value get: Dicta.items ()

6. Modify the value of the element in the dictionary: Dicta[keya] = value

7. Get the length of the Dictionary: Len (dicta)

8. Adding elements to the dictionary: dicta[key_new] = value

9. Delete all elements of the Dictionary: Dicta.clear ()

10. Delete the entire dictionary: del dicta

11. Dictionary combination: Dict (dicta, **DICTB) dicta.update (DICTB)

Four. Example

1. Dictionary definition, the dictionary key name can only be a number, a string, a tuple, and can not be repeated

STU1 = {"name":"Mr. Tease","Sex":"male"," Age": 20,"Hobby":"Run"}Print(STU1) Result: {'Sex':'male','Hobby':'Run','name':'Mr. Tease',' Age': 20}

2. Dictionary value: Dicta[keya] Dicta.get (Keya)

STU1 = {"name":"Mr. Tease","Sex":"male"," Age": 20,"Hobby":"Run"}Print(stu1["name"])Print(Stu1.get ("name") Results: Mr. Tease Mr. Tease

3. Modify Dictionary value: Dicta[keya] = Value,keya is already existing key

STU1 = {"name":"Mr. Tease","Sex":"male"," Age": 20,"Hobby":"Run"}stu1["name"] ="Mr. Little Tease"Print(STU1) Result: {'Hobby':'Run',' Age': 20,'name':'Mr. Little Tease','Sex':'male'}

4. Add a key-value pair to the dictionary, dicta[key_new] = Value,key_new is not present

STU1 = {"name":"Mr. Tease","Sex":"male"," Age": 20,"Hobby":"Run"}stu1["study"] ="python"Result: {' Age': 20,'study':'python','name':'Mr. Tease','Sex':'male','Hobby':'Run'}

5. Get the length of the Dictionary: Len (dicta)

 stu1 = { " name   ": "  mr. Tease   ", "  sex   ": "  male   ", "  age  : "   Hobby   ": "   Run   }   Print   (Len (STU1)) Results:  4 

6. A combination of two dictionaries: Dicta.update (DICTB) dict (dicta, **DICTB)

B = {"name":"Xiaojian"," Age": 28,"Is_marry": False} B.update ({"role":"Teacher","class":"python"})Print(B) Result: {'class':'python','Is_marry': False,' Age': 28,'role':'Teacher','name':'Xiaojian'}

B = {"name":"Xiaojian"," Age": 28,"Is_marry": False} C= {"role":"Teacher","class":"python"}d= Dict (B, * *C)Print(D) Result: {'class':'python','Is_marry': False,' Age': 28,'role':'Teacher','name':'Xiaojian'}

7. Delete all the elements in the Dictionary: Dicta.clear (), just empty the dictionary

A = {"name""Jack""sex""  M"}a.clear ()print(a) result: {}

8. Delete the entire dictionary: del dicta

A = {"name":"Jack","Sex":"M"}delaPrint(a) Result: Traceback (most recent): File"<pyshell#5>", Line 1,inch<module>Print(a) Nameerror:name'a'  is  notDefined

Lists and dictionaries in Python (ii)