我尝试使用字典作为switch语句，从用户输入调用各种方法。然而，似乎正在发生的是，无论用户选择什么方法，它都会按方法在我的字典中的列出顺序遍历所有方法，而不是在特定的方法调用之后退出。
我是python新手，使用过java，它有一个switch语句，并且能够在switch中使用break关键字，而python没有。
我在stackoverflow和google上到处搜索，没有找到任何关于我的特殊问题的线索，所以任何帮助都将不胜感激。
完整代码如下：

import pymysql

# Open DB

db = pymysql.connect()

# Prepare a cursor object using  cursor() method

cursor = db.cursor()

# Create a Student Table

cursor.execute("DROP TABLE IF EXISTS Student")
cursor.execute("CREATE TABLE Student(Id INT PRIMARY KEY AUTO_INCREMENT, Name VARCHAR(25))")

# Method for inserting new student mySQL

def insert() :
    name = input('Enter the Students name: ')
    instatmt = "INSERT INTO Student VALUES(NULL, '%s')" % (name)
    cursor.execute(instatmt)
    db.commit()

    return(print("Successfully inserted student"))

# Method for updating a student record mySQL

def update() :
    name = input('Enter the Students name: ')
    update = input('Enter the Updated name: ')

    upstatmt = "UPDATE Student SET Name='%s' WHERE Name='%s'" % (update, name)
    cursor.execute(upstatmt)
    db.commit()

    return(print("Successfully updated object"))

# Method for deleting a student record mySQL

def delete() :
    name = input('Enter the Students name: ')

    delstatmt = "DELETE FROM Student WHERE Name ='%s'" % (name)
    cursor.execute(delstatmt)
    db.commit()

    return(print("Successfully deleted object"))

# Method for retrieving a student record mySQL

def retrieve() :
    name = input('Enter the Students name: ')

    retstatmt = "SELECT * FROM Student WHERE Name ='%s'" % (name)
    display = cursor.execute(retstatmt)
    print(display)

    return(print("Object Retrieved..."))

# Call method requested by user

def performAction(argument):

    switcher = {
        'I': insert(),
        'U': update(),
        'D': delete(),
        'R': retrieve(),
        'E': exit
    }
    func = switcher.get(argument, lambda: "Invalid Entry")
    print (func)

# while True :

action = input('Which Operation would you like to perform ( I : Insert, U : Update, D: Delete, R: Retrieve, E: Exit): ')
performAction(action)

# disconnect from server

db.close()