What exactly is contained within a obj.__closure__? Question: Beazley pg 100 mentions: >>>python.__closure__ (<cell at 0x67f50: str object at 0x69230>,) >>>python.__closure__[0].cell_contents my understanding is that __closure__ is a list but what’s all this cell stuff and str object?? That looks like a 1-ary tuple? Asked By: user621819 || Source Answers: It is the new Python …
Python lambda closure scoping Question: I am trying to use closures to eliminate a variable from a function signature (the application is to make writing all the functions needed for connecting Qt signals for an interface to control a largish number of parameters to the dictionary that stores the values ). I do not understand …
Closures and Loops in Python Question: Suppose I have the following code callbacks = [] for i in range(10): callbacks.append(lambda x: i) all functions in callbacks will return the final value of i. How can I create callbacks that return the current value for i at creation time? Asked By: duckworthd || Source Answers: for …
Local variables in nested functions Question: Okay, bear with me on this, I know it’s going to look horribly convoluted, but please help me understand what’s happening. from functools import partial class Cage(object): def __init__(self, animal): self.animal = animal def gotimes(do_the_petting): do_the_petting() def get_petters(): for animal in [‘cow’, ‘dog’, ‘cat’]: cage = Cage(animal) def pet_function(): …
Python lambda's binding to local values Question: The following code spits out 1 twice, but I expect to see 0 and then 1. def pv(v) : print v x = [] for v in range(2): x.append(lambda : pv(v)) for xx in x: xx() I expected python lambdas to bind to the reference a local variable …
Function closure performance Question: I thought that I improve performance when I replace this code: def f(a, b): return math.sqrt(a) * b result = [] a = 100 for b in range(1000000): result.append(f(a, b)) with: def g(a): def f(b): return math.sqrt(a) * b return f result = [] a = 100 func = g(a) for …
Why does this UnboundLocalError occur (closure)? Question: What am I doing wrong here? counter = 0 def increment(): counter += 1 increment() The above code throws an UnboundLocalError. Asked By: Randomblue || Source Answers: To modify a global variable inside a function, you must use the global keyword. When you try to do this without …
Python's nonlocal depends on level of hierarchy? Question: This question is a follow-up on a question about Python variable scope. Additional questions q1, q2 and answers can be found on SO, among even more. The official Python documentation, and PEP 3104 are supposed to explain the details, but they don’t seem fully self-explanatory to me. …
In Python 2, how do I write to variable in the parent scope? Question: I have some code like: def example(): # other logic omitted stored_blocks = {} def replace_blocks(m): block = m.group(0) block_hash = sha1(block) stored_blocks[block_hash] = block return ‘{{{%s}}}’ % block_hash num_converted = 0 def convert_variables(m): name = m.group(1) num_converted += 1 return …
How to access (and edit) variables from a callback function? Question: I use Boto to access Amazon S3. And for file uploading I can assign a callback function. The problem is that I cannot access the needed variables from that callback function until I make them global. In another hand, if I make them global, …
