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0

I'm learning about client-server communication in python, and I want to send some packed structures.I want to pack a mathematical sign and a number. I tried like this:

idx = 50 
value1 = "<"
value2 = idx
packer = struct.Struct('1s I')
packed_data = packer.pack(*value1, *value2)

But I got the error:

packed_data = packer.pack(*value1, *value2)
TypeError: 'int' object is not iterable

or this error:

packed_data = packer.pack(*value1, *value2)
struct.error: argument for 's' must be a bytes object

If I try like this:

 value2 = [idx]

I don't know how to do this correctly.

python python-3.x int iterable pack

share|improve this question

edited Mar 23 at 13:12

Gábor

asked Mar 23 at 12:58

GáborGábor

876

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Why is the packing necessary? I think what you need is serialization, not packing. have a look at JSON.dumps()
  
  – g_uint
  Mar 23 at 13:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You don't need the *; it's just packer.pack(value1, value2).
  
  – chepner
  Mar 23 at 13:19
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @chepner also the struct.error: argument for 's' must be a bytes object error
  
  – Gábor
  Mar 23 at 13:23
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yeah, that's why I posted an answer instead of voting to close as "could no longer be reproduced".
  
  – chepner
  Mar 23 at 13:24
  
  

  
  
  
  

add a comment | 

0

I'm learning about client-server communication in python, and I want to send some packed structures.I want to pack a mathematical sign and a number. I tried like this:

idx = 50 
value1 = "<"
value2 = idx
packer = struct.Struct('1s I')
packed_data = packer.pack(*value1, *value2)

But I got the error:

packed_data = packer.pack(*value1, *value2)
TypeError: 'int' object is not iterable

or this error:

packed_data = packer.pack(*value1, *value2)
struct.error: argument for 's' must be a bytes object

If I try like this:

 value2 = [idx]

I don't know how to do this correctly.

python python-3.x int iterable pack

share|improve this question

edited Mar 23 at 13:12

Gábor

asked Mar 23 at 12:58

GáborGábor

876

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Why is the packing necessary? I think what you need is serialization, not packing. have a look at JSON.dumps()
  
  – g_uint
  Mar 23 at 13:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You don't need the *; it's just packer.pack(value1, value2).
  
  – chepner
  Mar 23 at 13:19
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @chepner also the struct.error: argument for 's' must be a bytes object error
  
  – Gábor
  Mar 23 at 13:23
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yeah, that's why I posted an answer instead of voting to close as "could no longer be reproduced".
  
  – chepner
  Mar 23 at 13:24
  
  

  
  
  
  

add a comment | 

I'm learning about client-server communication in python, and I want to send some packed structures.I want to pack a mathematical sign and a number. I tried like this:

idx = 50 
value1 = "<"
value2 = idx
packer = struct.Struct('1s I')
packed_data = packer.pack(*value1, *value2)

But I got the error:

packed_data = packer.pack(*value1, *value2)
TypeError: 'int' object is not iterable

or this error:

packed_data = packer.pack(*value1, *value2)
struct.error: argument for 's' must be a bytes object

If I try like this:

 value2 = [idx]

I don't know how to do this correctly.

python python-3.x int iterable pack

share|improve this question

edited Mar 23 at 13:12

Gábor

asked Mar 23 at 12:58

GáborGábor

876

idx = 50 
value1 = "<"
value2 = idx
packer = struct.Struct('1s I')
packed_data = packer.pack(*value1, *value2)

packed_data = packer.pack(*value1, *value2)
TypeError: 'int' object is not iterable

packed_data = packer.pack(*value1, *value2)
struct.error: argument for 's' must be a bytes object

 value2 = [idx]

share|improve this question

edited Mar 23 at 13:12

Gábor

asked Mar 23 at 12:58

GáborGábor

876

share|improve this question

edited Mar 23 at 13:12

Gábor

asked Mar 23 at 12:58

GáborGábor

876

asked Mar 23 at 12:58

GáborGábor

876

asked Mar 23 at 12:58

GáborGábor

876

1 Answer
1

active

oldest

votes

0

The first problem is that you are unnecessarily trying to (sequence-)unpack your arguments. The Struct format expects a bytes and an int, and you (almost) already have them.

The second problem is that "<" is a Unicode string, and pack expects bytes instead. You need to properly encode the string first.

packed_data = packer.pack(value1.encode('utf-8'), value2)

The particular encoding you use doesn't matter, as long as you use the same one to unpack the data.

Note that if you did have a Unicode character that couldn't be encoded in one byte, your string format would be wrong. The struct module doesn't handle variable-length strings by itself, so it would probably be simpler to just encode the int by itself and concatenated that with your encoded string.

value = 
packed_data = value1.encode('utf-8') + struct.pack("I", value2)

share|improve this answer

edited Mar 23 at 13:30

answered Mar 23 at 13:22

chepnerchepner

268k38258351

add a comment | 

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0

The first problem is that you are unnecessarily trying to (sequence-)unpack your arguments. The Struct format expects a bytes and an int, and you (almost) already have them.

The second problem is that "<" is a Unicode string, and pack expects bytes instead. You need to properly encode the string first.

packed_data = packer.pack(value1.encode('utf-8'), value2)

The particular encoding you use doesn't matter, as long as you use the same one to unpack the data.

Note that if you did have a Unicode character that couldn't be encoded in one byte, your string format would be wrong. The struct module doesn't handle variable-length strings by itself, so it would probably be simpler to just encode the int by itself and concatenated that with your encoded string.

value = 
packed_data = value1.encode('utf-8') + struct.pack("I", value2)

share|improve this answer

edited Mar 23 at 13:30

answered Mar 23 at 13:22

chepnerchepner

268k38258351

add a comment | 

0

The first problem is that you are unnecessarily trying to (sequence-)unpack your arguments. The Struct format expects a bytes and an int, and you (almost) already have them.

The second problem is that "<" is a Unicode string, and pack expects bytes instead. You need to properly encode the string first.

packed_data = packer.pack(value1.encode('utf-8'), value2)

The particular encoding you use doesn't matter, as long as you use the same one to unpack the data.

Note that if you did have a Unicode character that couldn't be encoded in one byte, your string format would be wrong. The struct module doesn't handle variable-length strings by itself, so it would probably be simpler to just encode the int by itself and concatenated that with your encoded string.

value = 
packed_data = value1.encode('utf-8') + struct.pack("I", value2)

share|improve this answer

edited Mar 23 at 13:30

answered Mar 23 at 13:22

chepnerchepner

268k38258351

add a comment | 

The first problem is that you are unnecessarily trying to (sequence-)unpack your arguments. The Struct format expects a bytes and an int, and you (almost) already have them.

The second problem is that "<" is a Unicode string, and pack expects bytes instead. You need to properly encode the string first.

packed_data = packer.pack(value1.encode('utf-8'), value2)

The particular encoding you use doesn't matter, as long as you use the same one to unpack the data.

Note that if you did have a Unicode character that couldn't be encoded in one byte, your string format would be wrong. The struct module doesn't handle variable-length strings by itself, so it would probably be simpler to just encode the int by itself and concatenated that with your encoded string.

value = 
packed_data = value1.encode('utf-8') + struct.pack("I", value2)

share|improve this answer

edited Mar 23 at 13:30

answered Mar 23 at 13:22

chepnerchepner

268k38258351

packed_data = packer.pack(value1.encode('utf-8'), value2)

value = 
packed_data = value1.encode('utf-8') + struct.pack("I", value2)

share|improve this answer

edited Mar 23 at 13:30

answered Mar 23 at 13:22

chepnerchepner

268k38258351

answered Mar 23 at 13:22

chepnerchepner

268k38258351

answered Mar 23 at 13:22

chepnerchepner

268k38258351