You should be using the dirpath which you call root. The dirnames are supplied so you can prune it if there are folders that you don’t wish os.walk to recurse into. import os result = [os.path.join(dp, f) for dp, dn, filenames in os.walk(PATH) for f in filenames if os.path.splitext(f)[1] == ‘.txt’] Edit: After the latest … Read more
How do you empty a vase containing five flowers? Answer: if the vase is not empty, you take out one flower and then you empty a vase containing four flowers. How do you empty a vase containing four flowers? Answer: if the vase is not empty, you take out one flower and then you empty … Read more
1. How is safely defined? Semantically. In this case, this is not a hard-defined term. It just mean “You can do that, without risk”. 2. If a program can be safely executed concurrently, does it always mean that it is reentrant? No. For example, let’s have a C++ function that takes both a lock, and … Read more
Use find: find . -name \*.txt -print On systems that use GNU find, like most GNU/Linux distributions, you can leave out the -print.
Remember that log(n!) = log(1) + log(2) + … + log(n-1) + log(n) You can get the upper bound by log(1) + log(2) + … + log(n) <= log(n) + log(n) + … + log(n) = n*log(n) And you can get the lower bound by doing a similar thing after throwing away the first half … Read more
Loops may achieve a performance gain for your program. Recursion may achieve a performance gain for your programmer. Choose which is more important in your situation!
No, and it never will since Guido van Rossum prefers to be able to have proper tracebacks: Tail Recursion Elimination (2009-04-22) Final Words on Tail Calls (2009-04-27) You can manually eliminate the recursion with a transformation like this: >>> def trisum(n, csum): … while True: # Change recursion to a while loop … if n … Read more
Java 8 provides a nice stream to process all files in a tree. Files.walk(Paths.get(path)) .filter(Files::isRegularFile) .forEach(System.out::println); This provides a natural way to traverse files. Since it’s a stream you can do all nice stream operations on the result such as limit, grouping, mapping, exit early etc. UPDATE: I might point out there is also Files.find … Read more
It doesn’t run forever. Each stack overflow causes the code to move to the finally block. The problem is that it will take a really, really long time. The order of time is O(2^N) where N is the maximum stack depth. Imagine the maximum depth is 5 foo() calls foo() calls foo() calls foo() calls … Read more
This depends on the language being used. You wrote ‘language-agnostic’, so I’ll give some examples. In Java, C, and Python, recursion is fairly expensive compared to iteration (in general) because it requires the allocation of a new stack frame. In some C compilers, one can use a compiler flag to eliminate this overhead, which transforms … Read more