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 On Wed, Apr 24, 2013 at 1:30 PM, Prasad, Ramit <ramit.pra...@jpmorgan.com>wrote: > sparkle Plenty wrote: > > Sent: Wednesday, April 24, 2013 11:52 AM > > To: Tutor@python.org > > Subject: [Tutor] Concatenating numeric data in Python 3.3 > > > > What is the best way to concatenate packed numeric data? I am building > a message to send to a device > > and it has a very specific header format and variable length payload. > Converting to string, > > concatenating, and then converting back to numeric introduced errors. > The tuple() function also > > introduced errors. > > > > The code is proprietary so I am not comfortable posting it. I have been > programming in Python for a > > few weeks. It is my first OOP language. My background, in the dim and > distant past, is mainframe. > > > > Any help would be greatly appreciated. Thank you in advance. > > Try reducing the error section to the minimal amount of code (or create > example that > has the same problem) and post that. > > Converting back and forth between strings and numeric types is often a > sign of smelly > code. Why do you need to convert back and forth? Not that conversion is > bad, just a > sign of a possible design problem. > > Repeated string concatenation can be a slow and wasteful procedure. > Use str's join method to build a string. > > >>> ','.join( [ 'a','b','c'] ) # Argument to join must be an iterable > (list/set/etc) > 'a,b,c' # of strings. Convert data to str before > joining. > >>> ' '.join( [ 'a','b','c'] ) > 'a b c' > > > ~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. >
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