Merge branch 'master' into 3.0

satwikkansal · satwikkansal · commit 43355e2498e6 · 2019-10-28T19:34:20.000+05:30
diff --git a/README.md b/README.md
@@ -2932,7 +2932,7 @@ nan
 
 #### 💡 Explanation:
 
-`'inf'` and `'nan'` are special strings (case-insensitive), which when explicitly typecasted to `float` type, are used to represent mathematical "infinity" and "not a number" respectively.
+`'inf'` and `'nan'` are special strings (case-insensitive), which when explicitly typecast-ed to `float` type, are used to represent mathematical "infinity" and "not a number" respectively.
 
 ---
 
@@ -2964,13 +2964,29 @@ nan
   + `++a` parses as `+(+a)` which translates to `a`. Similarly, the output of the statement `--a` can be justified.
   + This StackOverflow [thread](https://stackoverflow.com/questions/3654830/why-are-there-no-and-operators-in-python) discusses the rationale behind the absence of increment and decrement operators in Python.
 
+* Have you ever heard about _the space-invader operator_ in Python?
+  ```py
+  >>> a = 42
+  >>> a -=- 1
+  >>> a
+  43
+  ```
+  It is used as an alternative incrementation operator, together with another one
+  ```py
+  >>> a +=+ 1
+  >>> a
+  >>> 44
+  ```
+  **💡 Explanation:**
+  This prank comes from [Raymond Hettinger's tweet](https://twitter.com/raymondh/status/1131103570856632321?lang=en). The space invader operator is actually just a malformatted `a -= (-1)`. Which is equivalent to `a = a - (- 1)`. Similar for the `a += (+ 1)` case.
+
 * Python uses 2 bytes for local variable storage in functions. In theory, this means that only 65536 variables can be defined in a function. However, python has a handy solution built in that can be used to store more than 2^16 variable names. The following code demonstrates what happens in the stack when more than 65536 local variables are defined (Warning: This code prints around 2^18 lines of text, so be prepared!):
      ```py
      import dis
      exec("""
      def f():
          """ + """
-         """.join(["X"+str(x)+"=" + str(x) for x in range(65539)]))
+         """.join(["X" + str(x) + "=" + str(x) for x in range(65539)]))
 
      f()
 
