+## Pragmatism
+
+Early versions of _Black_ used to be absolutist in some respects. They took after its
+initial author. This was fine at the time as it made the implementation simpler and
+there were not many users anyway. Not many edge cases were reported. As a mature tool,
+_Black_ does make some exceptions to rules it otherwise holds. This section documents
+what those exceptions are and why this is the case.
+
+### The magic trailing comma
+
+_Black_ in general does not take existing formatting into account.
+
+However, there are cases where you put a short collection or function call in your code
+but you anticipate it will grow in the future.
+
+For example:
+
+```py3
+TRANSLATIONS = {
+ "en_us": "English (US)",
+ "pl_pl": "polski",
+}
+```
+
+Early versions of _Black_ used to ruthlessly collapse those into one line (it fits!).
+Now, you can communicate that you don't want that by putting a trailing comma in the
+collection yourself. When you do, _Black_ will know to always explode your collection
+into one item per line.
+
+How do you make it stop? Just delete that trailing comma and _Black_ will collapse your
+collection into one line if it fits.
+
+### r"strings" and R"strings"
+
+_Black_ normalizes string quotes as well as string prefixes, making them lowercase. One
+exception to this rule is r-strings. It turns out that the very popular
+[MagicPython](https://github.com/MagicStack/MagicPython/) syntax highlighter, used by
+default by (among others) GitHub and Visual Studio Code, differentiates between
+r-strings and R-strings. The former are syntax highlighted as regular expressions while
+the latter are treated as true raw strings with no special semantics.
+
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