How do I calculate a mean with python?

[William Bryant]

Ok I think I've fixed it thanks I read everything.

'''**************************************************************************'''
#* Name:        Mode-Median-Mean Calculator                                   *#
#*                                                                            *#
#* Purpose:     To calculate the mode, median and mean of a list of numbers   *#
#*              and the mode of a list of strings because that is what we are *#
#*              learning in math atm in school :P                             *#
#*                                                                            *#
#* Author:      William Bryant                                                *#
#*                                                                            *#
#* Created:     11/09/2013                                                    *#
#*                                                                            *#
#* Copyright:   (c) William 2013                                              *#
#*                                                                            *#
#* Licence:     IDK :3                                                        *#
'''**************************************************************************'''



#-----#                   ~~Import things I am using~~                   #-----#

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import time
import itertools



#-----#        ~~Variables that I am using, including the list.~~        #-----#

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List = []
NumberOfXItems = []

#-----#                   ~~Functions that I am using.~~                 #-----#

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def HMNs():
    global TheStr, user_inputHMNs, List_input, List
    user_inputHMNs = input("You picked string. This program cannot calculate the mean or median, but it can calculate the mode. :D  How many strings are you using in your list? (Can not be a decimal number)  \nEnter:  ")
    user_inputHMNs
    time.sleep(1.5)
    TheStr = int(user_inputHMNs)
    for i in range(TheStr):
        List_input = input("Enter your strings. (One in each input field):  ")
        List.append(List_input)
        print("Your list -> ", List)
        if List.count == int(user_inputHMNs):
            break
        print("\n*Mode*:", mode())
        print("*Median*:",  "<Coming soon!>\n")
        print("*Mean*:",    mean())

def HMNn():
    global TheNum, user_inputHMNn, List_input, List
    user_inputHMNn = input("You picked number. :D How many numbers are you using in your list? (Can not be a decimal number) \nEnter:  ")
    user_inputHMNn
    time.sleep(1.5)
    TheNum = int(user_inputHMNn)
    for i in range(TheNum):
        List_input = input("Enter your numbers. (One in each input field):  ")
        List_input = int(List_input)
        List.append(List_input)
        print("\nYour list -> ", List)
        if List.count == int(user_inputHMNn):
            break
        print("\n*Mode*:", mode())
        print("*Median*:",  "<Coming soon!>")
        print("*Mean*:",    mean())

def NOS():
    while True: # Loops forever (until the break)
        answer = input("Does your list contain a number or a string?  \nEnter: ")
        answer = answer.lower()
        if answer in ("string", "str", "s"):
            HMNs()
            break
        elif answer in ("number", "num", "n", "int"):
            HMNn()
            break
        elif answer in ("quit", "q"):
            break  # Exits the while loop
        else:
            print("You did not enter a valid field, :P Sorry.  \nEnter: ")
    time.sleep(1.5)

def mean():
    thesum = sum(List)
    amount = len(List)
    themean = thesum / amount
    return themean

def mode():
    max_occurrences = 0
    themode = None
    for i in List:
        thecount = List.count(i)
        if thecount > max_occurrences:
            max_occurrences = thecount
            themode = i
    return themode



#-----#               ~~The functions which need calling~~               #-----#

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NOS()