从用户输入的列表中删除名称，并平均成绩

Question

I've read lots of tutorials on Python and am currently in an intro to programming class using python, but I can't figure this out. I've searched stack overflow, dani web, java2s, github and many others but can't understand what I'm doing wrong.

This is for a final project in my programming class and I'd like to do a couple of things in class and then import them into the main program.

Eventually I hope to use this in my workplace as well and I want it to present the user with a menu of options. 1: Add names and typing speeds. 2: delete a name by value(the name of a student -- I'd like to do this with a class if possible. 3: print the names and speeds. 4: print a list of the speeds. 5: print the average speeds from the list of speeds (which I'd also like to do in a class). and 6 to quit the program.

I tried to be ambitious and create a random name generator so I created a function to print the list of names as well, but this is due Monday morning so I scrapped that project since I wasn't getting anywhere.

The parts that aren't working are #2 - deleting a name and #3 - averaging the score. On #2, I haven't had any luck trying .remove, del, or any other things I've seen people try. It seems most of examples are only hard coded in. The others don't make sense to me. On #3, I've tried multiple calculations including adding the numbers together separately, creating different functions and dividing by len and I've tried the mean built_in.

I can turn the assignment in based on what is working, but the other pieces would be especially helpful for when it is used for a purpose.

Here is my class program:

class student_info:

    def __init__(self):
        self.name = ""
        self.speed = ""
        self.speed_average = 0

def speed_average(self):
    return sum(self.speed) / len(self.speed)

and the main program (with comments):

import studentClass

name_list = []
speed = 0

def edit_list(name):
    new_name = input("What is the student's name? ")
    if new_name != "":
        name.name = new_name

    while True:
        try:
            typing_speed = input("What was the last typing speed? ")
            if speed != "":
                name.speed = float(typing_speed)
                #print (test_score)
            else:
                raise ValueError
            break
        except ValueError:
            print("Not a valid score.")

def print_students(list):
    for i, n in enumerate(list):
        print("#%d: Name: %s, Typing Speed (wpm): %d" % (i+1, n.name, n.speed))

def print_speed(list):
    for i, n in enumerate(list):
        print("%s" % (n.speed))

##Since the class instantiation didn't work, I tried creating a function - that didn't work either.
def print_avg(list):
    speed_list = speed
    print(sum(speed)/len(speed))

while True:
    print("Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit")
    choice = input(" >> ")
    if choice == '1':
        name_list.append(studentClass.student_info())
        edit_list(name_list[-1])
    elif choice == '2':
        names = [name_list]       
        del_name = input("What name would you like to remove? ")
        name_list.remove(del_name)
        if del_name not in name_list:
            print("Name not found.")
        else:
            print("%s removed." % del_name)
    elif choice == '3':
        print_students(name_list)           
    elif choice == '4':
        print_speed(name_list)
    elif choice == '5':
        class_avg = studentClass.student_info()
        print("Average score for class: " %(class_avg.speed_average))
    elif choice == '6':
        print('Happy Typing!')
        break
    else:
        print("That's not an option. Please try again.")



Error returned when #2 is selected:
Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit
 >> 1
What is the student's name? john
What was the last typing speed? 20
Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit
 >> 1
What is the student's name? mary
What was the last typing speed? 10
Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit
 >> 4
20.0
10.0
Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit
 >> 3
#1: Name: john, Typing Speed (wpm): 20
#2: Name: mary, Typing Speed (wpm): 10
Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit
 >> 2
What name would you like to remove? john
Traceback (most recent call last):
  File "C:\Users\Whited\Desktop\Classes\Programming\studentRun.py", line 44, in <module>
    name_list.remove(del_name)
ValueError: list.remove(x): x not in list
>>>



Error returned when #5 is selected:

    Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit
     >> 1
    What is the student's name? john
    What was the last typing speed? 20
    Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit
     >> 1
    What is the student's name? mary
    What was the last typing speed? 10
    Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit
     >> 5
    Traceback (most recent call last):
      File "C:\Users\Whited\Desktop\Classes\Programming\studentRun.py", line 56, in <module>
        print("Average score for class: " %(class_avg.speed_average))
    TypeError: not all arguments converted during string formatting
    >>> 

Everything else is running as it should. If anyone can help me out with this I'd sure appreciate it. Thank you!

UPDATE: running 5 with proper indentation and call.

Traceback (most recent call last): File "C:\\Users\\Whited\\Desktop\\Classes\\Programming\\studentRun.py", line 56, in print("Average score for class: " %(class_avg.speed_average())) TypeError: 'int' object is not callable

UPDATE: Using Python 3 by the way. - And, the file is saved as studentClass

Answer 1

I am bored, and a little buzzed, so I thought I would just throw out some working code that you might be able to learn from:

# A Student object will just take care of tracking the name and speed.
# Classes like this in Python (with no methods) are often better represented
# by a namedtuple from the collections package.
class Student(object):

    def __init__(self, name="", speed=0):
        self.name = name
        self.speed = speed

# The Class object will represent a group of students.
# The students are tracked via a dictionary where the key is the name of 
# the student and the value is the Student object.
class Class(object):

    def __init__(self):
        """ Create an empty dictionary for the students """
        self.students = {}

    def add_student(self, student):
        """ Add a student to the "roster".  The student name will be the 
            key and the Student instance will be the value """
        self.students[student.name] = student

    def remove_student(self, name):
        """ Remove a student if they exist.  If they exist and are removed
            return True.  If they do not exist, return False """
        if name in self.students:
            del self.students[name]
            return True
        return False

    def average(self):
        """ Get the average speed of the students.
            The self.student.values() will be the values of the self.students
            dictionary, which means it will be a list of students.
            For each of the students, get their speed.  Sum those speeds
            and divide by the number of students.
            The fancy syntax of [x for x in y] below is called a list comprehension """
        return sum(student.speed for student in self.students.values()) / len(self.students)

def print_students(group):
    for i, student in enumerate(group.students.values()):
        print("#%d: Name: %s, Typing Speed (wpm): %d" % (i+1, student.name, student.speed))

def print_speed(group):
    for i, student in enumerate(group.students.values()):
        print("#%d: Typing Speed (wpm): %d" % (i+1, student.speed))


def add_student(group):
    new_name = ""
    typing_speed = None
    while not new_name:
        new_name = input("What is the student's name? ")
    while typing_speed in ("", None):
        typing_speed = input("What was the last typing speed? ")
        try:
            typing_speed = float(typing_speed)
        except:
            print("Please enter a number")
            typing_speed = None
            continue
    # We have a valid name and value speed, so create a Student and add them to the Class
    group.add_student(Student(new_name, typing_speed))


if __name__ == "__main__":
    group = Class()

    while True:
        print("Hi user, (1) add (2) delete (3) print (4) print scores (5) print average (6) quit")
        choice = input(" >> ")

        if choice == '1':
            add_student(group)
            continue

        if choice == '2':
            del_name = input("What name would you like to remove? ")
            if group.remove_student(del_name):
                print("%s removed." % del_name)
            else:
                print("Name not found.")
            continue

        if choice == '3':
            print_students(group)
            continue

        if choice == '4':
            print_speed(group)
            continue

        if choice == '5':
            print("Average score for class: %0.2f" %(group.average()))
            continue

        if choice == '6':
            print('Happy Typing!')
            break

        print("That's not an option. Please try again.")

I prefer the if => continue in this case instead of the if, elif...

Using a Class (poorly named) to manage the students (addition and removal) and take their average is a pretty good approach.

As far as what you did wrong:

1. Deleting a student.

You name_list isn't a list of names, it is a list of student_info . You try to remove the name from the list before checking if it is in there, so this will always fail. At the very least you would want to check for existence before calling remove . But that would never work for you because the list does not contain strings, it contains student_info . To make yours work you would need to do something like

found = False
for i, student in enumerate(name_list):
    if student.name == del_name:
        found = i
if found != False:
    del name_list[found]
    print("Deleted...")
else:
    print("Could not find name %s" % (del_name,))

2. Taking the average:

What you were doing is creating a new, empty instance of student_info. What you want to do is get the values of the students that exist.

total_score = 0
for student in name_list:
    total_score += student.speed
average = total_score / len(name_list)

In response to your questions in the comment:

1. All classes should inherit from object (New Style Classes) https://wiki.python.org/moin/NewClassVsClassicClass

2. values is a way to get the values of a dictionary.

   {"1": ['a', 'b'], "foo", 10.0}.values() == [["a", "b"], 10.0]

3. Just copy the Student and Class classes into another file (say models.py for instance) and either:

   import models

And then everywhere you use a Student or Class (outside of models.py) you prefix them with models. Like

group = models.Class()
...
group.append(models.Student(new_name, typing_speed))

Or you could just have

from models import *

This would import everything from models.py into the current namespace so no other code would need to change. Keeping the namespace is a good idea... so I would go for option 1.

4. The name == main thing...

if __name__ == "__main__"

It is good practice to include this in every file. When you execute a python program the file you execute has a name of " main ". This check will tell you whether you were the file being executed. If your file was imported by something else then name would not be " main ". This allows for you to do different things depending on whether you were executed or imported.

Answer 2

I think you could have used a dictionary for this problem.

Also you have a member speed_average and a member function speed_average. Have a different names for the function and the variable.