[README.md] Improve documentation on safe metadata extraction and add more examples

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Sergey M․ 2018-11-05 00:11:36 +07:00
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@ -1168,7 +1168,28 @@ title = self._search_regex(
### Use safe conversion functions ### Use safe conversion functions
Wrap all extracted numeric data into safe functions from `utils`: `int_or_none`, `float_or_none`. Use them for string to number conversions as well. Wrap all extracted numeric data into safe functions from [`youtube_dl/utils.py`](https://github.com/rg3/youtube-dl/blob/master/youtube_dl/utils.py): `int_or_none`, `float_or_none`. Use them for string to number conversions as well.
Use `url_or_none` for safe URL processing.
Use `try_get` for safe metadata extraction from parsed JSON.
Explore [`youtube_dl/utils.py`](https://github.com/rg3/youtube-dl/blob/master/youtube_dl/utils.py) for more useful convenience functions.
#### More examples
##### Safely extract optional description from parsed JSON
```python
description = try_get(response, lambda x: x['result']['video'][0]['summary'], compat_str)
```
##### Safely extract more optional metadata
```python
video = try_get(response, lambda x: x['result']['video'][0], dict) or {}
description = video.get('summary')
duration = float_or_none(video.get('durationMs'), scale=1000)
view_count = int_or_none(video.get('views'))
```
# EMBEDDING YOUTUBE-DL # EMBEDDING YOUTUBE-DL