A vanilla version of REPL is 10 lines of python. Session runs waiting for input unless user exits the shell. Any valid input after ">>> " is echoed back to the user.
While this works for newline and command line, there is an error here.
import sys
import readline
def main():
while True:
sys.stdout.write(">>> ")
sys.stdout.flush()
command_line = input().strip() # trim leading/trailing spaces
if not command_line:
continue
print(f"You entered: {command_line}") # return the input back to user
if __name__ == "__main__":
main()
Pressing ctrl+c returns the (intended) KeyboardInterrupt error but exits the shell instead of ignoring the malformed input.
We add this behavior in an exception block. If the shell gets crtl+c, it should inform the user of KeyboardInterrupt and conveniently wait for the next input ">>> ". Let's go one step further and add EOFError handling when shell sees ctrl+d.
The below change handles these exceptions:
try:
command_line = input().strip()
if not command_line:
continue
print(f"You entered: {command_line}")
except KeyboardInterrupt:
print("\nKeyboardInterrupt")
break
except EOFError:
print()
continue
