I’m assuming you want to know about CPython, the standard implementation. Python 2 and Python 3.0-3.2 use either UCS2* or UCS4 for Unicode characters, meaning it’ll either use 2 bytes or 4 bytes for each character. Which one is picked is a compile-time option. \u2049 is then represented as either \x49\x20 or \x20\x49 or \x49\x20\x00\x00 … Read more
Note: exec was just a Simple statement in Python 2.x, whereas it is a function in Python 3.x. Python 2.7 Let us check the changes made by executing a. class Test: def __init__(self): l, g = locals().copy(), globals().copy() exec a # NOT a function call but a statement print locals() == l, globals() == g … Read more
One important thing about this behavior is that Python caches some, mostly, short strings (usually less than 20 characters but not for every combination of them) so that they become quickly accessible. One important reason for that is that strings are widely used in Python’s source code and it’s an internal optimization to cache some … Read more
This helps the interpreter assure that the keys for class-level attributes and methods can only be strings. Elsewhere, Python is a “consenting adults language”, meaning that dicts for objects are exposed and mutable by the user. However, in the case of class-level attributes and methods for classes, if we can guarantee that the keys are … Read more
There are two different characters involved here. One is the MICRO SIGN, which is the one on the keyboard, and the other is GREEK SMALL LETTER MU. To understand what’s going on, we should take a look at how Python defines identifiers in the language reference: identifier ::= xid_start xid_continue* id_start ::= <all characters in … Read more
This isn’t about using inplace += versus + binary add. You didn’t tell us the whole story. Your original version concatenated 3 strings, not just two: sTable = sTable + ‘\n’ + sRow # simplified, sRow is a function call Python tries to help out and optimises string concatenation; both when using strobj += otherstrobj … Read more
The .pyc files are created (and possibly overwritten) only when that python file is imported by some other script. If the import is called, Python checks to see if the .pyc file’s internal timestamp is not older than the corresponding .py file. If it is, it loads the .pyc; if it isn’t or if the … Read more
In an ideal world, you’d be right and some of the inconsistencies you found would be wrong. However, CPython has optimized some scenarios, specifically function locals. These optimizations, together with how the compiler and evaluation loop interact and historical precedent, lead to the confusion. Python translates code to bytecodes, and those are then interpreted by … Read more
For an OrderedDict it’s inherently O(n) because the ordering is recorded in a linked list. For the builtin dict, there’s a vector (a contiguous array) rather than a linked list, but pretty much the same thing in the end: the vector contains a few kind of “dummies”, special internal values that mean “no key has … Read more
Read the reference manual, it’s in there. Specifically: Multiple adjacent string or bytes literals (delimited by whitespace), possibly using different quoting conventions, are allowed, and their meaning is the same as their concatenation. Thus, “hello” ‘world’ is equivalent to “helloworld”. This feature can be used to reduce the number of backslashes needed, to split long … Read more