[README.md] Move code from #21939 to the right place

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Sergey M 2019-08-02 05:54:56 +07:00 committed by GitHub
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@ -1216,6 +1216,72 @@ Incorrect:
'PLMYEtVRpaqY00V9W81Cwmzp6N6vZqfUKD4'
```
### Inline values
Extracting variables is acceptable for reducing code duplication and improving readability of complex expressions. However, you should avoid extracting variables used only once and moving them to opposite parts of the extractor file, which makes reading the linear flow difficult.
#### Example
Correct:
```python
title = self._html_search_regex(r'<title>([^<]+)</title>', webpage, 'title')
```
Incorrect:
```python
TITLE_RE = r'<title>([^<]+)</title>'
# ...some lines of code...
title = self._html_search_regex(TITLE_RE, webpage, 'title')
```
### Collapse fallbacks
Multiple fallback values can quickly become unwieldy. Collapse multiple fallback values into a single expression via a list of patterns.
#### Example
Good:
```python
description = self._html_search_meta(
['og:description', 'description', 'twitter:description'],
webpage, 'description', default=None)
```
Unwieldy:
```python
description = (
self._og_search_description(webpage, default=None)
or self._html_search_meta('description', webpage, default=None)
or self._html_search_meta('twitter:description', webpage, default=None))
```
Methods supporting list of patterns are: `_search_regex`, `_html_search_regex`, `_og_search_property`, `_html_search_meta`.
### Trailing parentheses
Always move trailing parentheses after the last argument.
#### Example
Correct:
```python
lambda x: x['ResultSet']['Result'][0]['VideoUrlSet']['VideoUrl'],
list)
```
Incorrect:
```python
lambda x: x['ResultSet']['Result'][0]['VideoUrlSet']['VideoUrl'],
list,
)
```
### Use convenience conversion and parsing functions
Wrap all extracted numeric data into safe functions from [`youtube_dl/utils.py`](https://github.com/ytdl-org/youtube-dl/blob/master/youtube_dl/utils.py): `int_or_none`, `float_or_none`. Use them for string to number conversions as well.