Python, 请大神帮我看下，怎样做才能在执行完一个if语句后不退出程序，而是回到我写的菜单？

Question

import sys
import numpy as np
from functions import *

print("|",format("\033[1;36m  Welcome to Bacteria Analyzing \033[0m","*^60"),"|")
print("\n Please select the action you want to take:")
print("\n 1. Load data")
print("\n 2. Filter data")
print("\n 3. Diaplay statistics")
print("\n 4. Generate plots")
print("\n 5. Quit")
    
user_option=int(input("The action you want to take: "))

data = np.loadtxt("valid_data.txt")



def filter_data():
        global bacteria
        bacteria=int(input("What kind of bacteria you want to analise? (Type in NA if you don't want to filter bacteria)  "))
        global groRate_l
        groRate_l=float(input("lower limit: "))
        global groRate_h
        groRate_h=float(input("higner limit: "))
        print(("The bacteria you want to check is""\033[1;35m {0}\033[0m").format(bacteria))
        print(("The growth range you want to check is ""\033[1;35m[{:f},{:f}]\033[0m").format(groRate_l,groRate_h))
        
        global data_f
        data_f=data[((data[:,1]>groRate_l) & (data[:,1]<groRate_h) & (data[:,2]==bacteria))]


if user_option==1:
    try:
        file_name=str(input("Pease enter your file's name: "))
        dataLoad(file_name)
    except:
        print("\033[1;31m File not found, plesae check your spelling.\033[0m")
        
if user_option==2:
    filter_data()

if user_option==3:
    statistic = str(input("which statistic you want to perform? "))
    dataStatistics(data_f, statistic)
    

if user_option==5:
    print("Thank you for using, bye~")
    sys.exit()
  

还有怎么样定义一个全局变量：

Answer 1

import sys
import numpy as np
from functions import *
 
print("|",format("\033[1;36m  Welcome to Bacteria Analyzing \033[0m","*^60"),"|")
print("\n Please select the action you want to take:")
print("\n 1. Load data")
print("\n 2. Filter data")
print("\n 3. Diaplay statistics")
print("\n 4. Generate plots")
print("\n 5. Quit")
    
user_option=int(input("The action you want to take: "))
 
data = np.loadtxt("valid_data.txt")
 
 
 
def filter_data():
        global bacteria
        bacteria=int(input("What kind of bacteria you want to analise? (Type in NA if you don't want to filter bacteria)  "))
        global groRate_l
        groRate_l=float(input("lower limit: "))
        global groRate_h
        groRate_h=float(input("higner limit: "))
        print(("The bacteria you want to check is""\033[1;35m {0}\033[0m").format(bacteria))
        print(("The growth range you want to check is ""\033[1;35m[{:f},{:f}]\033[0m").format(groRate_l,groRate_h))
        
        global data_f
        data_f=data[((data[:,1]>groRate_l) & (data[:,1]<groRate_h) & (data[:,2]==bacteria))]
 
while True:
	if user_option == 1:
		try:
			file_name = str(input("Pease enter your file's name: "))
			dataLoad(file_name)
		except:
			print("\033[1;31m File not found, plesae check your spelling.\033[0m")
	
	if user_option == 2:
		filter_data()
	
	if user_option == 3:
		statistic = str(input("which statistic you want to perform? "))
		dataStatistics(data_f, statistic)
	
	if user_option == 5:
		print("Thank you for using, bye~")
		sys.exit()