通过Python中的输入循环

Question

I have a python script where we get the input from the USER (in the command window, no need for GUI window at this point). once the user provides the input, the provided input has to be validated and the if the input is in wrong format, the input needs to be asked again & again till the input is correct. The part of the script where user input is asked & validated is below & working absolutely fine.

SOname = '1'  #something that doesn't validate
while True:
    SOname = input("Please enter the order number: ").upper()
    if not re.match(r"\b[A-Z]{2}[-][0-9]{6}\b", SOname):
        print ("Error! Please enter order in format 'AS-XXXXXX'"
    else:
        break

After this condition is satisfied, the order number is used further to do a lot of activities. However, completing the rest of the program takes 2 minutes (it involves a lot of file copying, PDF reading etc...) & i do not want the user to keep waiting for the program to end and start again to enter another order number.

So, i want to provide the option of entering multiple order numbers separated by space(for ex: they can enter 5 order numbers & work on something else while the python program runs for 10-12mins). And just like for a single order number, each of the entries should be validated for the above mentioned criteria & each of the number should go through the rest of the program.

Here is where i am failing miserably. I wrote a small program to check if all the elements go through the loop and it does not & i cannot figure out why.

user_input = input("Enter Numbers:")
Ui = user_input.split()
for i in range(len(Ui)):
    if i == 2:
        print(i)
    else:
        print ("tada")

If it enter the values "2 4 2 4 2 4", i get the output " tada tada 2 tada tada tada"

it does not even makes sense to me. it prints 2 once but there are 3 2's in the input. What am i doing wrong? how do I make input to go through the validation, then through the rest of the program. And also, in a scenario when the user started the program but does not want to give an input , how to end the script by clicking Esc key?? I looked up in a lot of places but nothing is working for me.

Answer 1

The condition is over i which is the current index in the loop (because you iterated on range(len(Ui)) ), eg, it takes values from 0, 1, 2, and so on.

I guess you expected i to be the current value introduced by the user. If so, then the loop should be for i in Ui: instead. Notice however than this value is a string, not an integer (even if the input looks like an integer). So the comparison should be i == "2" (or int(i) == 2 , but this is not error-proof if the user enters something that cannot be converted by int ).

Answer 2

The variable i in the loop is not taking on the value of the data but the index into that data. So the first time through it will have a value of 0, the next time 1, etc. So you will always print out '2' as the second element no matter what your actual input.

If you want to iterate across the values of your list try:

for i in Ui:
   if int(i) == 2:
       print(i)

The int() is there because the input will be a string from the input, and not an integer.

A fuller example, using your regex validation would look like:

import re

while True:
    user_input = input("Enter Numbers:")
    Ui = user_input.split()
    for order in Ui:
        if not re.match(r"\b[A-Z]{2}[-][0-9]{6}\b", order):
            print ("Error! Please enter order in format 'AS-XXXXXX', not {}".format(order))
            break
    else:
        break

print("Orders are {}".format(", ".join(Ui)))

Answer 3

Firstly, regarding your second splitting code, you probably missed out type conversion.

In Python, 2 == '2' will return False .

So, to make the second part of your code work, this will help:

user_input = input("Enter Numbers:")
Ui = user_input.split()
for i in range(len(Ui)):
    if int(i) == 2:
        print(i)
    else:
        print ("tada")

Now, furthermore, your order IDs are seemingly in format AS-XXXXXX . In this case, you wouldn't have to do the int type-casting. Because your order IDs are anyway going to be String .

So for entering multiple order IDs, this might help (also, I have taken the liberty to add the ESC key exit which you wanted, even though I would say it's a whole topic in itself):

import keyboard    
while True:
    if keyboard.is_pressed('ESC'):
        break
    else:
        SOname = input("Please enter the order number:  (If multiple, seperate by spaces)").upper()
        if(SOname == 
        IDArray = SOname.split()
        for ID in IDArray:
            if not re.match(r"\b[A-Z]{2}[-][0-9]{6}\b", ID):
            print ("Error in ", ID, " Please enter order in format 'AS-XXXXXX'")
        else:
            break

For using keyboard , you might want to pip install keyboard in your shell.