用python打印字典中的条目

Question

I have a dictionary and I am trying to get a code to print using a function. I am having trouble getting my function to work and not understanding why it isn't printing the student from my dictionary.

def getstudent(key):
    students = {'23A' :['Apple', 'John', 95.6],
                '65B' :['Briton', 'Alice', 75.5],
                '56C' :['Terling', 'Mary', 98.7],
                '68R' :['Templeton', 'Alex', 90.5]}

I want to then run the function and type in getstudent('65B'), but when I run I don't get anything in return.

Thanks!

Answer 1

You are not using the key parameter or returning anything in your function:

def getstudent(key):
    students = {'23A' :['Apple', 'John', 95.6],
                '65B' :['Briton', 'Alice', 75.5],
                '56C' :['Terling', 'Mary', 98.7],
                '68R' :['Templeton', 'Alex', 90.5]}
    return students.get(key) # return 

print(getstudent('65B'))
['Briton', 'Alice', 75.5]

Or forget about the function and just access the dict directly with students.get(key) .

You might also want to output an informative message if the key does not exist which can be done by passing a default value to get:

students.get(key,"Key does not exist")

Answer 2

Without any error checking:

def getstudent(key):
    students = {'23A' :['Apple', 'John', 95.6],
                '65B' :['Briton', 'Alice', 75.5],
                '56C' :['Terling', 'Mary', 98.7],
                '68R' :['Templeton', 'Alex', 90.5]}
    print(students[key])

getstudent('65B')

Answer 3

try like this

def getstudent(key):
    students = {'23A' :['Apple', 'John', 95.6],
                '65B' :['Briton', 'Alice', 75.5],
                '56C' :['Terling', 'Mary', 98.7],
                '68R' :['Templeton', 'Alex', 90.5]}
   if key in students.keys():     # to handle if key is not present
       return students[key]
   else: return "No key found"
getstudent('65B')

output:

['Briton', 'Alice', 75.5]

you need to return the value

How dictionary works, dictionary has a pair that is called, key and its value . The value of dictionary can be fetched by its key value. so what i am doing here. when you call a function with key. I am fetching the value based on key ie students[key] it will give you value of key in your dictionary.
students.keys() will give you list of all key in a dictionary

Answer 4

def getstudent(key):
    students = {'23A' :['Apple', 'John', 95.6],
                '65B' :['Briton', 'Alice', 75.5],
                '56C' :['Terling', 'Mary', 98.7],
                '68R' :['Templeton', 'Alex', 90.5]}
    if key in students:
        return students[key]
    else:
        return "%s is not a valid key" % (key)

If you run getstudent('65B') you will get a list

['Briton', 'Alice', 75.5]

you can then access the list by indexing eg

a_student = getstudent('65B')   # now a_student list is as ['Briton', 'Alice', 75.5]
print a_student[0]

a_student[0] prints 'Briton'