Input function not working in python script [duplicate]

Question

I am a python newcomer and have problem with executing my input code. My code is as follows:

userInput = input("Hi, What is your name? ") 
print("Welcome {0}, Nice to meet you!".format(userInput))

Now the problem is that it runs perfectly fine in PyCharm 2020, yet when I try to run it in my Ubuntu 20.04's terminal, it returns the following error:

./userIO.py: line 7: syntax error near unexpected token `('
./userIO.py: line 7: `userInput = input("Hi, What is your name? ")'

I wonder what could the cause be. Can you please help me find what can cause the problem?

Answer 1

When running scripts (e.g. by doing ./script at a command line), Linux uses a special line known as a shebang line to figure out what program is used to run the script. For example, #!/bin/bash for Bash scripts, or #!/usr/bin/env python3 for Python scripts.

If there is no shebang line, Bash will default to running the script in Bash (i.e. as a shell script). Since your script is not a shell script, you get a bunch of errors from Bash attempting to interpret your Python code as a shell script.

To fix this, you need a shebang line, which must be the first line of your script. For a Python 3 script, you may use #!/usr/bin/env python3, e.g. as follows:

#!/usr/bin/env python3
userInput = input("Hi, What is your name? ") 
...

Alternatively, you can fix this by explicitly running your script with the Python interpreter, e.g. python3 script.py.

Answer 2

Thanks to all friends especially nneonneo I can solve my problem in either of the two ways as below:

1. If running it as a python script without using a shebang (so that the OS can understand how to run it), I can run the script correctly by typing:

     me@linuxbox $> python3 userIO.py
   

2. If I like to be able to run the script by just typing ./userIO.py, then nneonneo's solution is the best.
   So to find the correct address to my python interpreter I typed: which python3 In my terminal and applied the terminal's return value (in my case it was: /usr/bin/python3) to the beginning of the file's contents as: #!/usr/bin/python3, so that I can now execute the file more easily.

Answer 3

You can change your second line of code with:

print(f"Welcome {userInput}, Nice to meet you!")

This reduces number of columns in your code.