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Python format hex number

I need to send a string via tcp. One of the first sections of the string is the length of the command variable
Example:
command = STATUS?UPDATE
I need to send the following string below
sendCommand = '\x00\x00\x00'+STRINGLENGTH+'\x02'+command+'\x0D\x0A'
My string length is 11 so I need STRINGLENGTH to be the hex equivalent of 11, which is 0xB, except that I need it to output as \x0B
Padding it with the leading 0 is easy, but I cannot get it to output as \x instead of 0x, and if I do a string replace it is treated as text and not as hex, so it doesn't work.
My final hex string should be:
\x00\x00\x00\x0B\x02\x53\x54\x41\x54\x55\x53\x3f\x55\x53\x45\x52\x0D\x0A
I am instead getting:
\x00\x00\x000x0B\x02\x53\x54\x41\x54\x55\x53\x3f\x55\x53\x45\x52\x0D\x0A
Any ideas on how to format it correctly?

So, this is a bit of a round-about fashion, but use a bytes object:
>>> STRINGLENGTH = bytes([11]).decode()
>>> endCommand = '\x00\x00\x00'+STRINGLENGTH+'\x02'
>>> endCommand
'\x00\x00\x00\x0b\x02'
Almost certainly, you are going to want to change your str object back to a bytes object, but the above should get you going.
I suspect what you were doing was using the hex function:
>>> STRINGLENGTH = hex(11)
>>> endCommand = '\x00\x00\x00'+STRINGLENGTH+'\x02'
>>> endCommand
'\x00\x00\x000xb\x02'
The fundamental thing you need to understand is that you aren't working with "hex", you are working with bytes. Hex is just how bytes are traditionally represented. The hex helper function returns a hexadecimal representation, as a string of an integer. But that isn't what you want. You want the byte corresponding to the value 11.
Note, for the ascii-range, chr(i) might works as well, so
>>> STRINGLENGTH = chr(11)
>>> endCommand = '\x00\x00\x00'+STRINGLENGTH+'\x02'
>>> endCommand
'\x00\x00\x00\x0b\x02'
But be careful, say you wanted the number 129, you have to care about the encoding...
>>> chr(129)
'\x81'
But in bytes, in UTF-8, that's actually represented by two different bytes
>>> chr(129).encode()
b'\xc2\x81'
>>> list(chr(129).encode())
[194, 129]
Which of course, depends on the encoding:
>>> chr(129).encode('latin')
b'\x81'
>>> list(chr(129).encode('latin'))
[129]
>>>
For that reason, I think it is safer to stick with the slightly wordier:
>>> bytes([129])
b'\x81'

How do I convert hex to utf-8?

I want to convert a hex string to utf-8
a = '0xb3d9'
to
동 (http://www.unicodemap.org/details/0xB3D9/index.html)

First, obtain the integer value from the string of a, noting that a is expressed in hexadecimal:
a_int = int(a, 16)
Next, convert this int to a character. In python 2 you need to use the unichr method to do this, because the chr method can only deal with ASCII characters:
a_chr = unichr(a_int)
Whereas in python 3 you can just use the chr method for any character:
a_chr = chr(a_int)
So, in python 3, the full command is:
a_chr = chr(int(a, 16))

How to remove '\x' from a hex string in Python?

I'm reading a wav audio file in Python using wave module. The readframe() function in this library returns frames as hex string. I want to remove \x of this string, but translate() function doesn't work as I want:
>>> input = wave.open(r"G:\Workspace\wav\1.wav",'r')
>>> input.readframes (1)
'\xff\x1f\x00\xe8'
>>> '\xff\x1f\x00\xe8'.translate(None,'\\x')
'\xff\x1f\x00\xe8'
>>> '\xff\x1f\x00\xe8'.translate(None,'\x')
ValueError: invalid \x escape
>>> '\xff\x1f\x00\xe8'.translate(None,r'\x')
'\xff\x1f\x00\xe8'
>>>
Any way I want divide the result values by 2 and then add \x again and generate a new wav file containing these new values. Does any one have any better idea?
What's wrong?

Indeed, you don't have backslashes in your string. So, that's why you can't remove them.
If you try to play with each hex character from this string (using ord() and len() functions - you'll see their real values. Besides, the length of your string is just 4, not 16.
You can play with several solutions to achieve your result:
'hex' encode:
'\xff\x1f\x00\xe8'.encode('hex')
'ff1f00e8'
Or use repr() function:
repr('\xff\x1f\x00\xe8').translate(None,r'\\x')

One way to do what you want is:
>>> s = '\xff\x1f\x00\xe8'
>>> ''.join('%02x' % ord(c) for c in s)
'ff1f00e8'
The reason why translate is not working is that what you are seeing is not the string itself, but its representation. In other words, \x is not contained in the string:
>>> '\\x' in '\xff\x1f\x00\xe8'
False
\xff, \x1f, \x00 and \xe8 are the hexadecimal representation of for characters (in fact, len(s) == 4, not 24).

Use the encode method:
>>> s = '\xff\x1f\x00\xe8'
>>> print s.encode("hex")
'ff1f00e8'

As this is a hexadecimal representation, encode with hex
>>> '\xff\x1f\x00\xe8'.encode('hex')
'ff1f00e8'

Python String of Hex to Hex (with leading zeros)

I have some issue with hex conversion in Python.
I have a string that represents a hex number - "02" and I want to convert it to 0x02 and to join it to another hex number.
My code:
valToWrite1 = '\x3c'
valToWrite2 = '02'
I want to join those 2 values so that my result will be "\x3c\x02".
It's important to keep the leading zeros.

You need binascii.unhexlify():
>>> import binascii
>>> binascii.unhexlify("02")
'\x02'
>>> '\x3c' + _
'<\x02'

hex string to character in python

I have a hex string like:
data = "437c2123"
I want to convert this string to a sequence of characters according to the ASCII table.
The result should be like:
data_con = "C|!#"
Can anyone tell me how to do this?

In Python2
>>> "437c2123".decode('hex')
'C|!#'
In Python3 (also works in Python2, for <2.6 you can't have the b prefixing the string)
>>> import binascii
>>> binascii.unhexlify(b"437c2123")
b'C|!#'

In [17]: data = "437c2123"
In [18]: ''.join(chr(int(data[i:i+2], 16)) for i in range(0, len(data), 2))
Out[18]: 'C|!#'
Here:
for i in range(0, len(data), 2) iterates over every second position in data: 0, 2, 4 etc.
data[i:i+2] looks at every pair of hex digits '43', '7c', etc.
chr(int(..., 16)) converts the pair of hex digits into the corresponding character.
''.join(...) merges the characters into a single string.

Since Python 2.6 you can use simple:
data_con = bytes.fromhex(data)

The ord function converts characters to numerical values and the chr function does the inverse. So to convert 97 to "a", do ord(97)