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# Converting 2bit hex representation to integer ?

 P: n/a Hi I am using binascii.b2a_hex to convert some binary data to hex. The result is a two bit hex representation (i. e., without the leading hex). How do I convert the resulting two bit representation into an integer ? Thanks. Oct 19 '05 #1
6 Replies

 P: n/a Can you give us an example. I don't know what two bit hex means (takes at least 4 bits to make a hex digit). Now I'm going to try to guess: If the data is binary then all you need to do is to use the struct.unpack module to convert to integer. Larry Bates Madhusudan Singh wrote: Hi I am using binascii.b2a_hex to convert some binary data to hex. The result is a two bit hex representation (i. e., without the leading hex). How do I convert the resulting two bit representation into an integer ? Thanks. Oct 19 '05 #2

 P: n/a Larry Bates wrote: Can you give us an example. I don't know what two bit hex means (takes at least 4 bits to make a hex digit). Like 64(base 16)=100. I am referring to 64 in the above. Now I'm going to try to guess: If the data is binary then all you need to do is to use the struct.unpack module to convert to integer. Doesn't unpack presume that the input is a string ? If so, is it safe to convert binary data to string using str() ? Oct 19 '05 #3

 P: n/a Madhusudan Singh wrote: Larry Bates wrote: Can you give us an example. I don't know what two bit hex means (takes at least 4 bits to make a hex digit). Like 64(base 16)=100. I am referring to 64 in the above. Now I'm going to try to guess: If the data is binary then all you need to do is to use the struct.unpack module to convert to integer. Doesn't unpack presume that the input is a string ? If so, is it safe to convert binary data to string using str() ? Followup to this : I just tried : n=str(x) print struct.unpack("b",n) I get (51,) The corresponding output of binascii.b2a_hex(x) is 33. And 51_10=33_16. So that checks out. What is the deal with the parenthesis and the comma ? Oct 19 '05 #4

 P: n/a Madhusudan Singh wrote: Can you give us an example. I don't know what two bit hex means (takes at least 4 bits to make a hex digit). Like 64(base 16)=100. I am referring to 64 in the above. that's two digits, not two bits. print int("64", 16) 100 Now I'm going to try to guess: If the data is binary then all you need to do is to use the struct.unpack module to convert to integer. Doesn't unpack presume that the input is a string ? If so, is it safe to convert binary data to string using str() ? since Python uses string objects to hold binary data, that shouldn't be necessary. (struct also supports the CPython low-level buffer protocol, so it works with any type that sees itself as a string of bytes). Oct 19 '05 #5

 P: n/a No you can't convert using str(). Binary data is stored in a Python string object, but it isn't really a string. It is rather just a bunch of bits packed into a string variable. struct.unpack() will unpack those bits into any number of different types of variables and is what you need. Example: import struct s='\x64' values=struct.unpack('b',s) print "values=",values value=(100,) Note: struct.unpack returns a tuple of values. Just get values to get the first one. Larry Madhusudan Singh wrote: Larry Bates wrote:Can you give us an example. I don't know what two bithex means (takes at least 4 bits to make a hex digit). Like 64(base 16)=100. I am referring to 64 in the above.Now I'm going to try to guess:If the data is binary then all you need to do is touse the struct.unpack module to convert to integer. Doesn't unpack presume that the input is a string ? If so, is it safe to convert binary data to string using str() ? Oct 20 '05 #6

 P: n/a Madhusudan Singh wrote: I just tried n=str(x) print struct.unpack("b",n) I get (51,) What is the deal with the parenthesis and the comma ? If you really don't know what the parentheses and comma mean in the above output, I would suggest that you need to go back a step and walk through the Python tutorial before you try to continue on with what you are attempting to do. (Section 5.3 specifically covers your question.) Either that, or read the documentation on struct.unpack() since that describes what it returns fairly clearly. Assuming your input represents a C-style integer (i.e. fixed size) rather than a Python long integer (of arbitrary length), you should be able to use just struct.unpack('i', mybinarydata) to get the result you need... -Peter Oct 21 '05 #7

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