Create progress-bars.md

Python/progress-bars.md

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+# Progress bars for long-running loops or tasks
+
+If you have a loop that has a number of iterations or takes a long time to run, you can get an easy progress bar (with an estimated time to completion) using tools like [tqdm](https://tqdm.github.io/) or [Rich](https://rich.readthedocs.io/en/latest/progress.html). They also work in Jupyter notebooks.
+
+## tqdm
+
+Change your loop from:
+
+```python
+for i in range(10000):
+    ...
+```
+
+to:
+
+```python
+from tqdm import tqdm
+for i in tqdm(range(10000)):
+    ...
+```
+
+And get this for free:
+
+```
+76%|████████████████████████████         | 7568/10000 [00:33<00:10, 229.00it/s]
+```
+
+You can also manually update the progress bar in your code using [`tqdm.update()`](https://tqdm.github.io/docs/tqdm/#update).
+
+## Rich
+
+Rich works in a similar way, and also provides [rich console output](rich-console-output.md) more generally.