python-2.x

I am writing a module to let me write code in python 3, but still run it in 2. It looks surprisingly easy actually... anything else I should add? From my (limited) flailing on the interactive interpreter, the future imports do not affect python 3 and are viewed as redundant. # _2or3.py ''' Common usage: from __future__ import print_function, nested_scopes, division, absolute_import, unicode_literals from _2or3 import * ''' import sys if sys.version[0] == '2': range = xrange input = raw_input Obviously there are some things you cannot do that you would normally be able to do in 3 (like

I've realized that some methods should be called with () , while others can't. How can I check, using IPython e.g., whether to use parentheses or not? For example the following file scratch.py import numpy as np arr = np.random.randn(5) print arr.sort, "\n" print arr.sort(), "\n"; print arr.shape, "\n"; print arr.shape(), "\n"; produces this output: <built-in method sort of numpy.ndarray object at 0x7fb4b5312300> None (5,) Traceback (most recent call last): File "scratch.py", line 8, in <module> print arr.shape(), "\n"; TypeError: 'tuple' object is not callable Those are not methods, those are

On Python 2.7, for dir in os.listdir("E:/Library/Documents/Old - Archives/Case"): print dir prints out: Danny.xlsx Dannyh.xlsx ~$??? ?? ?????? ??? ???? ???????.docx while this: # using a unicode literal for dir in os.listdir(u"E:/Library/Documents/Old - Archives/Case"): print dir prints out: Dan.xlsx Dann.xlsx Traceback (most recent call last): File "E:\...\FirstModule.py", line 31, in <module> print dir File "C:\Python27\lib\encodings\cp1252.py", line 12, in encode return codecs.charmap_encode(input,errors,encoding_table) UnicodeEncodeError: 'charmap' codec can't encode characters in position

I have a very basic parrot script written in Python that simply prompts for a user input and prints it back inside an infinite loop. The Raspberry Pi has a USB barcode scanner attached for the input. while True: barcode = raw_input("Scan barcode: ") print "Barcode scanned: " + barcode When you scan at a "normal" speed it works reliably and the command output looks like this: Scan barcode: 9780465031467 Barcode scanned: 9780465031467 Scan barcode: 9780007505142 Barcode scanned: 9780007505142 But when you really hammer it with many scans in close succession it is possible to make it miss inputs

Why does hasattr say that the instance doesn't have a foo attribute? >>> class A(object): ... @property ... def foo(self): ... ErrorErrorError ... >>> a = A() >>> hasattr(a, 'foo') False I expected: >>> hasattr(a, 'foo') NameError: name 'ErrorErrorError' is not defined` The python2 implementation of hasattr is fairly naive, it just tries to access that attribute and see whether it raises an exception or not. Unfortunately, this means that any unhandled exceptions inside properties will get swallowed, and errors in that code can get lost. To add insult to injury, when hasattr eats the exception