On Wed, Apr 24, 2013 at 4:21 PM, Prasad, Ramit <ramit.pra...@jpmorgan.com>wrote:
> Thank you for not replying above, but please continue to CC the tutor list. > > sparkle Plenty wrote: > > > > On Wed, Apr 24, 2013 at 2:45 PM, Prasad, Ramit < > ramit.pra...@jpmorgan.com> wrote: > > Please post your response *after* the quoted context. > > > > sparkle Plenty wrote: > > > > > > Thanks to both of you for your assistance. > > > Since the completed message must be in hex, I also have an issue with > losing high order zeros during > > > conversions, although the binary shift works well for adding on to the > end of the string. I cannot > > > pack string data, and I cannot concatenate numbers, so the > conversions, although smelly, were what I > > > knew to try. I welcome the idea of abandoning that course of action. > It didn't work anyway. > > > > > > I will have an unknown number of instances, each of which consists of > 3 numeric values. I tried > > > packing each instance using struct.pack, then converting to a tuple, > then concatenating. This ran, > > > but introduced errors: in some instances, high order truncation of a > leading zero in the first of > > the > > > 3 values. This throws off the position of all data that follows. > Error messages and error code are > > > dependent on which technique is being tried. The most recent ones are: > > > TypeError: can't concat bytes to str > > > TypeError: Can't convert 'tuple' object to str implicitly > > > > > > > > Can you give us the format and samples of the input and the output? We > do not > > need real data, often you can just use data of the same type but change > values. > > > > If you need hex, you can turn numbers into hex str by using the hex() > built-in. > > > > >>> ''.join([hex(15), hex(1239393), hex(49494)]) > > '0xf0x12e9610xc156' # Need to handle formatting > > > > You may want to also look at the binascii module for some functions for > > converting data. Again, if you provide some sample output (and hopefully > input) > > then we can help you better. > > > > > > ~Ramit > > > > > > This email is confidential and subject to important disclaimers and > > conditions including on offers for the purchase or sale of > > securities, accuracy and completeness of information, viruses, > > confidentiality, legal privilege, and legal entity disclaimers, > > available at http://www.jpmorgan.com/pages/disclosures/email. > > > > Input is from a gui so the first value is obtained from the identifier > for the control the user > > changed: > > 1234 > > The second value is associated with the first. > > 01 > > The third value is, for instance, a switch on/off > > 01 or 00, let's say it's 00. > > > > the output for this instance would need to be > > 0x04d20x010x00. > > Are you sure you want the starting '0x' for each byte? > > > > > Here is my function as it stands now: > > > > def conCatNumbers(numOne, numTwo, numThree): > > global instanceGroup, lengthCounter, instanceCounter > > print("Pre Pack: ", numOne, " ", numTwo, " ", numThree) > > packValues = struct.pack("HBB", numOne, numTwo, numThree) > > print("Post Pack: ", packValues) > > instanceValues = (packValues, ) > > print(instanceValues) > > instanceGroup = (instanceGroup, ) > > instanceGroup = instanceGroup + instanceValues > > lengthCounter += 4 > > instanceCounter += 1 > > return (instanceGroup, lengthCounter, instanceCounter) > > > > It is the first function I have written, and it is an ugly little spud. > > Why are you using global variables? What purpose do they serve? > If you can provide the rationale for the global variables, chances > are we can suggest a better way to do that. I think you would be > better off having instanceGroup as a list and append to the list. > As it is right now instanceGroup is a weirdly nested list. Look at > difference between the following two sets of code and output. > > >>> blah = () > >>> def foo(): > ... global blah > ... instanceValues = ('\x04\xd2\x01\x00', ) > ... blah = (blah,) > ... blah = blah + instanceValues > ... print blah > ... > >>> foo() > ((), '\x04\xd2\x01\x00') > >>> foo() > (((), '\x04\xd2\x01\x00'), '\x04\xd2\x01\x00') > >>> foo() > ((((), '\x04\xd2\x01\x00'), '\x04\xd2\x01\x00'), '\x04\xd2\x01\x00') > >>> foo() > (((((), '\x04\xd2\x01\x00'), '\x04\xd2\x01\x00'), '\x04\xd2\x01\x00'), > '\x04\xd2\x01\x00') > >>> foo() > ((((((), '\x04\xd2\x01\x00'), '\x04\xd2\x01\x00'), '\x04\xd2\x01\x00'), > '\x04\xd2\x01\x00'), '\x04\xd2\x01\x00') > > >>> blah = [] > >>> def foo(): > ... instanceValues = '\x04\xd2\x01\x00' > ... blah.append( instanceValues ) # module level object can be mutated > without global keyword, > # just not reassigned (name binding). > ... print blah > ... > >>> foo() > ['\x04\xd2\x01\x00'] > >>> foo() > ['\x04\xd2\x01\x00', '\x04\xd2\x01\x00'] > >>> foo() > ['\x04\xd2\x01\x00', '\x04\xd2\x01\x00', '\x04\xd2\x01\x00'] > >>> foo() > ['\x04\xd2\x01\x00', '\x04\xd2\x01\x00', '\x04\xd2\x01\x00', > '\x04\xd2\x01\x00'] > > > Your struct.pack() line seems fine, but you might want to specify > endian-ness as the default value may vary by architecture. > (See http://en.wikipedia.org/wiki/Endian ) > > >>> struct.pack('>HBB', 1234,1,0 ) > '\x04\xd2\x01\x00' # note location of 4 and d2 > >>> struct.pack('<HBB', 1234,1,0 ) > '\xd2\x04\x01\x00' # note location of 4 and d2 are swapped > > > [copied from above] > > lengthCounter += 4 > > instanceCounter += 1 > > return (instanceGroup, lengthCounter, instanceCounter) > > It is seems like that you are using these to keep track of length > or iterating over them. If you switch to list you can do something like: > > for instance in instanceGroup: > do_task(instance) > for index, instance in enumerate(instanceGroup): # useful if you want to > know iteration number > do_task(instance) > if not index % 100: # log heartbeat every 100 iterations > print('Went through {} iterations'.format(index)) > instanceCounter = len(instanceGroup) > lengthCounter = instanceCounter*4 > > > ~Ramit > > > Thank you so much! I knew the Global statement was a cop-out, but I was frustrated with the endless Unbounded Local Variable errors, and getting a little wild-eyed and desperate as my project deadline approaches. I will implement the changes you suggested, and then retest. I have also searched the Tutor archives quite a lot, and noted a number of websites that I will peruse for another online course (I have taken the one at Python.org) so I can review class and function best practices. It is great to have someone to ask when I get stuck.
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