diff --git a/README.md b/README.md index 129de05..907ebdf 100644 --- 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()