progress-bar.md

Progress Bars

Basic progress bar

There are many progressbars out there for Python, but they are dependencies, and this can be really annoying, especially when it is hard to install pip libraries.

To make any progressbar, you need to know the string option \r. What makes \r unique is that it will go to the start of printing.

For example, if you were to do print('Hello World!'), it would print Hello World!. To visualize it, it is more like

Hello World!
            ^

The cursor is at the character after the !. If we were to use \r, the cursor would go to the front. In our example, it would mean

Hello World!
^

See how the cursor is at the h? If it were to print anything, it would overwrite the character h.

Theoretically, if we want to make a progressbar, we have to print a string multiple times with \r.

times = 1 # how many times the loop has looped
for i in range(10): # will repeat whatever is below 10 times.
    print('\rHappened '+str(times)+' times.') #happened x times
    times += 1 #this is the same as times = times + 1

However, if we run this, there will be an error. Each line will print on a new line.

Happened 1 times.
Happened 2 times.
Happened 3 times.
Happened 4 times.
Happened 5 times.
Happened 6 times.
Happened 7 times.
Happened 8 times.
Happened 9 times.
Happened 10 times.

This is because the print function adds \n to the end of every string that is printed. Theoretically, it is printing '\rHappened '+str(times)+' times.\n'. We do not want \n to be added, so to fix this, write print('\rHappened '+str(times)+' times.', end = ''). This makes it so that print will add '' to the end of every string, which is equal to nothing. Finally if you run

times = 1 # how many times the loop has looped
for i in range(10): # will repeat whatever is below 10 times.
    print('\rHappened '+str(times)+' times.', end = '') #happened x times
    times += 1 #this is the same as times = times + 1

You will get just one line of text. The only problem is that it happens so quickly, that you cannot see the bar updating. Try making it loop 1000000 times.

times = 1 # how many times the loop has looped
for i in range(1000000): # will repeat whatever is below 1000000 times.
    print('\rHappened '+str(times)+' times.', end = '') #happened x times
    times += 1 #this is the same as times = times + 1

Now you can see the text changing.

Finally, you want to make sure to run times = 1 every time you use this progressbar so that the number restarts at 1. You can also change the text to say whatever you want.

To do a basic x/total bar, just add a bit of text that says the total:

times = 1 # how many times the loop has looped
for i in range(1000000): # will repeat whatever is below 1000000 times.
    print('\rHappened '+str(times)+'/1000000 times.', end = '') #happened x times
    times += 1 #this is the same as times = times + 1

For basic programmers:

def basic_function():
    sum = 1+1

def counter(reps):
    times = 1
    for i in range(reps): # will repeat whatever is below reps times.
        basic_function()
        print('\rHappened '+str(times)+'/'+str(reps)+' times.', end = '') #happened x times
        times += 1 #this is the same as times = times + 1

counter(1000000)

Just replace whatever is in basic_function with whatever you want to happen

If you are on Python2, enter in from __future__ import print_function at the top of the file/first thing on your interpter

Using tqdm library

from tqdm import tqdm

alist = list(range(5))

for thing in tqdm(alist):
    print(thing)  # or whatever you do...

A few more examples:

from tqdm import tqdm, trange
import random
import time


def tqdm_example_1():
    for i in tqdm(range(10)):
        time.sleep(0.2)


def tqdm_example_2():
    for i in trange(10, desc="outer_loop"):
        for j in trange(10, desc="inner_loop"):
            time.sleep(0.01)


def tqdm_example_3(add_tot=False):
    max_iter = 100
    tot = 0

    if add_tot:
        bar = tqdm(desc="update example", total=max_iter)
    else:
        bar = tqdm()

    while tot < max_iter:
        update_iter = random.randint(1, 5)
        bar.update(update_iter)
        tot += update_iter
        time.sleep(0.03)


def tqdm_example_4():
    t = trange(100)
    for i in t:
        t.set_description(f"on iter {i}")
        time.sleep(0.02)


if __name__ == "__main__":
    # tqdm_example_1()
    # tqdm_example_2()
    # tqdm_example_3()
    # tqdm_example_3(True)
    tqdm_example_4()