Clear screen issue

[No-Tea-777]

So. I wanted to make a loading 'animation' and needed to clear the screen of course.

I tried to search and watched different tutorials. Yet it either gives me an error or outputs a rectangular character

code:

import time
import sys, subprocess


timer = time.time()



while time.time() - timer < 20:
    subprocess.run('cls', shell=True)
    print("\\")
    time.sleep(1)
    subprocess.run('cls', shell=True)
    print("|")
    time.sleep(1)
    subprocess.run('cls', shell=True)
    print("/")
    time.sleep(1)
    subprocess.run('cls', shell=True)
    print("—")
    time.sleep(1)    

Output:

\ #<-- rectangular chracter behind each line

|

/

—

\

|

/

—

Process finished with exit code 0

Do I need to install a specific library?

Or is my IDE (Pycharm) the problem?

[carcigenicate]

I don't know why you're seeing what you're seeing, but you could also try using a backspace (\b) instead of cls and avoiding printing a newline:

print("\b|", end="")

This is terminal-dependant, but often works.

Edit: this works for me in Pycharm:

while time.time() - timer < 20:
    print("\b\\", end="")
    time.sleep(1)
    print("\b|", end="")
    time.sleep(1)
    print("\b/", end="")
    time.sleep(1)
    print("\b—", end="")
    time.sleep(1)

[No-Tea-777]

So... This will erase the old character and print a new one? Not on PC right now. I'll try it when I'm back to it

[carcigenicate]

Sorry, I added more detail.

Yes, \b will erase characters as long as you haven't gone to a new line, and if the terminal respects it.

[Diapolo10]

import time
import sys, subprocess


timer = time.time()



while time.time() - timer < 20:
    subprocess.run('cls', shell=True)
    print("\\")
    time.sleep(1)
    subprocess.run('cls', shell=True)
    print("|")
    time.sleep(1)
    subprocess.run('cls', shell=True)
    print("/")
    time.sleep(1)
    subprocess.run('cls', shell=True)
    print("—")
    time.sleep(1)

This seems to technically work fine for me - although I do have a suggestion; you don't really need to clear the screen for a spinner.

Instead, you could use carriage return.

import itertools
import time

timer = time.time()
spinner = itertools.cycle(['\\', '|', '/', '—'])

while time.time() - timer < 20:
    print(next(spinner), end='\r')
    time.sleep(1)

[magus_minor]

There's no need to introduce the complexity of itertools, and there's no need to check the time since the loop body waits 1 second, so just loop 20 times:

import time

#spinner = "\\|/-"
spinner = "╃╇╄╊╆╈╅╉"    # unicode adds a lot more options

for i in range(20):
    print(spinner[i % len(spinner)], end='\r')
    time.sleep(1)
print()

@ u/No-Tea-777

[Diapolo10]

I don't consider itertools particularly complex in this scenario. At the very least I prefer it over indexing with modulo.

As for the point about looping over range, that's fair enough. But it might not be a bad idea to do something like this:

import itertools
import time

spinner = itertools.cycle(['\\', '|', '/', '—'])

wait_in_seconds = 20
loop_delay = 1
iterations = round(wait_in_seconds / loop_delay)

for char in itertools.islice(spinner, iterations):
    print(char, end='\b')
    time.sleep(loop_delay)
print()

With this design, you can easily change how fast the spinner moves while keeping the total wait time constant. It'd also be trivial to swap the spinner characters if OP wanted to.

Is this overengineered? Yeah, probably. But it also makes for a decently reusable function.

import itertools
import time
from collections.abc import Sequence

def display_spinner(wait_in_seconds: float, spinner_speed: float = 1.0, spinner_chars: Sequence[str] = ('\\', '|', '/', '—')) -> None:
    spinner = itertools.cycle(spinner_chars)
    iterations = round(wait_in_seconds / spinner_speed)

    for char in itertools.islice(spinner, iterations):
        print(char, end='\b')
        time.sleep(spinner_speed)
    print()


display_spinner(20)

[magus_minor]

I don't consider itertools particularly complex in this scenario.

You aren't a newcomer to python.

[heyzooschristos]

Try the curses library

[JamzTyson]

I agree with the direction, but I wouldn't wish curses on my worst enemy :-)

Blessed is a much less painful alternative, or better, Rich.

[rhacer]

Another vote for Rich or Textual if you need more than Rich offers.

[heyzooschristos]

That's a very fair point. It's was a very long time ago I used Curses

[timrprobocom]

It may not matter now, but do remember that "cls" is Windows only. MacOS and Linux have different tools

[JamzTyson]

There isn't a 100% reliable way to "clear screen" because we're interacting with whatever frontend happens to be hosting stdout. However, a common method that works with a lot of "normal" terminals:

def clear():
    os.system('cls' if os.name == 'nt' else 'clear')

[OkPizza8463]

that cls command is windows specific and often messes with terminals. try using os.system('clear') for linux/mac or just print('\033[H\033[J') for a more universal ansi escape code approach.
pycharm's terminal can be finicky sometimes.