Why is Pycharm failing to convert string to integer?

Question

num = 0
for i in range(5):
    ask = int(input())
    if abs(ask) > 0:
        num = ask

print(num)

When I run the code, it lets me input the first string. But once I enter the second string, the program crashes and says "pythonProject\main.py", line 3, in ask = int(input()) ValueError: invalid literal for int() with base 10: ''"

What's going on?

My input: I just type 1, press enter, type 2, press enter and then it crashes. I am sure it is not an error where I click enter too quickly, or I accidentally type in an empty string because I've ran the code multiple times.

What have I tried so far?

• Creating a new project and pasting the code -> didn't work
• Asking my friend to copy the code onto his PyCharm and run it -> worked fine on his computer
• 'Edit configurations', uncheck 'emulate code in output console' -> didn't work, it was already unchecked
• Checked that I was running the correct file in the project -> didn't work, I was running the right file

EDIT:

• FIXED, just needed to check 'Emulate code in output console' rather than uncheck it. Not sure why this works though, or how I can keep it checked for all future projects - rather than having to manually check it every time.

Answer 1

FIXED, just needed to check 'Emulate code in output console' rather than uncheck it. Not sure why this works though, or how I can keep it checked for all future projects - rather than having to manually check it every time.

Answer 2

The problem is with the input, as you are either pressing enter without any input (empty string) or you are entering a float value. This thread might help you in this case. The code is working fine when I input an integer and gives the same error when entered empty string or a float value.

Answer 3

To get it work you need to check "Emulate code in output console". I've answered in the comments section and I'm glad it worked out, here is an explanation:

You need to know a concept of "terminal emulator" to understand why and how this works. When a program is ran (at least on UNIX-like operating systems), it has three I/O streams: stdin, stdout and stderr. The stdin is used to input data, and two others are for output.

Input or output stream is just a buffer used to communicate with the program back and forth. Once something is written to the buffer, it can be read from there. If the buffer is empty, an attempt to read from there will cause stall until the buffer has something in it. More about stdio: https://en.wikipedia.org/wiki/Standard_streams

When the program is ran through the terminal emulator, I/O streams are connected to this emulator, so whatever you type in the terminal window is written to your stdin by default. Whatever your program writes to the stdout and stderr is displayed on the screen. (However, this behavior may be changed using pipes, so you can pass data from some file to the stdin and also you can redirect the output to the file)

Here is the history behind terminal emulators, to understand, why is it implemented this way: https://en.wikipedia.org/wiki/Terminal_emulator#Computer_terminals

For example, you have a simple program:

s = input('Enter string: ')
print(f'stdout: {s}')

If you run it from the terminal and type "TEST":

$ python3 test.py
TEST
stdout: TEST

But you also can, for example, pass data directly to stdin, and redirect output to the file:

$ echo "ABCDEF" | python3 test.py > OUTPUT.txt

there will be no text in the terminal, but OUPUT.txt will appear. It will contain:

stdout: ABCDEF

Now, about PyCharm: By default, when it runs your script, it does not automatically emulate terminal in the output window. It simply does not send anything to the stdin and it won't react to pressed keys. When your program gets to the line with input(), it starts to read the stdin stream until it gets \n character from the stream (indicating that user has pressed Return key). As nothing gets sent to the stream, it will wait infinitely.

Useful tip: for testing, instead of just typing something into the terminal every time, you can also check "Redirect input from:" and choose an input file.