How to Get Python to Detect for No Input

How do I get python to recognize that there has been no input

I think this is what you're looking for

try:
    some = int(input("Enter a number"))
    print("Good job")
except (SyntaxError, ValueError):
    print("You didn't enter a number")

How to detect if input is not given in a python program

What you're looking for is the try-except block. See the following for an example:

input_invalid = true
while input_invalid:
    user_input = input("Enter position: ")
    try:
        user_input = int(user_input)
        input_invalid = false
    except ValueError:
        print("Please enter a valid integer!")

Here, the try-except block catches any errors (of the type specified
in except) thrown within the code block. In this case, the error results from trying to call int() on a string that does not contain an integer (ValueError). You can use this to explicitly prevent the error and control the logic flow of your program like shown above.

An alternate solution without using try-except is to use the .isdigit() method to validate the data beforehand. If you were to use .isdigit() (which I personally think is better), your code would look something like this:

input_invalid = true
while input_invalid:
    user_input = input("Enter position: ")
    if user_input.isdigit():
        input_invalid = false
    else:
        print("Please enter a valid integer!")

Hope this helped!

How to handle no input using input() function in Python?

Since you are using python 2, use raw_input() instead of input().

tmp=raw_input("Choose program type:1.C++;2.Python;3.PERL (ENTER for default 2.Python)")
...
...
if tmp!='':
    tmp = int(tmp)
    pass #do your stuff here
else:
    pass #no user input, user pressed enter without any input.

The reason you are getting error is because in python2 input() tries to run the input statement as a Python expression.

So, when user gives no input, it fails.

How do I check if user input has entered nothing?

at the last of the if statement, you forgot to print the middlename. That's why it's not printing anything. Another thing, you don't need to use replace method, instead you can simply use middlename = "Z". And the last one, there's no need to use else statement. just type the if statement and its functions and then break out of the if statement and then print the middlename.

Full code:

if middlename == "":
    middlename = "Z"
print(middlename)

Python stop input after empty string is entered

You're passing the result of input() directly into append(), with no intermediate step to check if it's empty.

You need to save the input in a separate variable and check if it's empty before appending it to your list.

Try this:

while True:
    answer = input("Enter values: ")
    if not answer:
        break
    lista.append(answer)
return lista

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