string-interning

Does Python have a pool of all strings and are they (strings) singletons there? More precise, in the following code one or two strings were created in memory: a = str(num) b = str(num) ? Strings are immutable in Python, so the implementation can decide whether to intern (that's a term often associated with C#, meaning that some strings are stored in a pool) strings or not. In your example, you're dynamically creating strings. CPython does not always look into the pool to detect whether the string is already there - it also doesn't make sense because you first have to reserve memory in order to

I see a lot of legacy code like this: class A { public static final String CONSTANT = "value".intern(); ... } I don't see any reason for the intern(), as in the Javadoc one can read: "All literal strings and string-valued constant expressions are interned." Is there some intent of this, maybe in past revisions of the language? kdgregory This is a technique to ensure that CONSTANT is not actually a constant. When the Java compiler sees a reference to a final static primitive or String, it inserts the actual value of that constant into the class that uses it. If you then change the constant

In Java, explicitly declared Strings are interned by the JVM, so that subsequent declarations of the same String results in two pointers to the same String instance, rather than two separate (but identical) Strings. For example: public String baz() { String a = "astring"; return a; } public String bar() { String b = "astring" return b; } public void main() { String a = baz() String b = bar() assert(a == b) // passes } My question is, does CPython (or any other Python runtime) do the same thing for strings? For example, if I have some class: class example(): def __init__(): self._inst =

This question already has an answer here: About the changing id of an immutable string 5 answers >>> s1 = "spam" >>> s2 = "spam" >>> s1 is s2 True >>> q = 'asdalksdjfla;ksdjf;laksdjfals;kdfjasl;fjasdf' >>> r = 'asdalksdjfla;ksdjf;laksdjfals;kdfjasl;fjasdf' >>> q is r False How many characters should have to s1 is s2 give False ? Where is limit? I.e., I am asking how long a string has to be before python starts making separate copies of it. String interning is implementation specific and shouldn't be relied upon, use equality testing if you want to check two strings are identical. If you want,

I want to know the process and internals of string interning specific to .Net framework . Would also like to know the benefits of using interning and the scenarios/situations where we should use string interning to improve the performance. Though I have studied interning from the Jeffery Richter's CLR book but I am still confused and would like to know it in more detail. [Editing] to ask a specific question with a sample code as below: private void MethodA() { string s = "String"; // line 1 - interned literal as explained in the answer //s.intern(); // line 2 - what would happen in line 3 if