what is the simplest way to print the result as follows using pyhton3
I have a Hex string s="FFFC"
In python if using this command line: print(int(s,16))
The result I'm expecting is -4 (which is in signed format). But this is not the case, It displays the Unsigned format which the result is 65,532.
How can I convert this the easiest way?
Thank you in advance.
There are several ways, but you could just do the math explicitly (assuming s has no more than 4 characters, otherwise use s[-4:]):
i = int(s, 16)
if i >= 0x8000:
i -= 0x10000
You can use the bytes.fromhex and int.from_bytes class methods.
s = bytes.fromhex('FFFC')
i = int.from_bytes(s, 'big', signed=True)
print(i)
Pretty self-explanatory, the only thing that might need clarification is the 'big' argument, but that just means that the byte array s has the most significant byte first.
Related
I have a python string that looks like this:
byte_string = "01100110"
I want to turn this into a byte like so:
byte_byte = some_function(byte_string) # byte_byte = 0b01100110
How can I achieve this?
It appears you want to turn that string into a single number. For that you just convert to int with a base of 2.
byte_byte = int(byte_string, 2)
After reflecting on the question some more, I think I originally mis-understood your intent, which is reflected in my below "Prior Answer".
I'm thinking this prior SO question may address your question as well, as it sounds like you want to convert a string of 8 bits into a single byte.
And, as #Mark Ransom has indicated, it would look like this as a decimal code:
int(byte_string, 2)
output: 102
Or like this as the corresponding ascii character:
chr(int(byte_string, 2))
output: 'f'
----Prior Answer Based on Assumption of Encoding a String into an array of bytes------
You can encode a string to bytes like this, optionally passing the specific encoding if you want:
byte_string = "01100110"
byte_string.encode("utf-8")
bytes(byte_string, 'utf-8')
Result:
b'01100110'
Link to python docs for encoding / decoding strings.
Another option would be to create a bytearray:
bytearray(byte_string, 'utf-8')
output: bytearray(b'01100110')
And here is another StackOverflow thread that might be helpful as well, describing the difference between bytes and bytearray objects in relation to their use in converting to and from strings.
Can anyone tell me how to convert a float number to 32-bit binary string and from a 32-bit binary string to a float number in python?
'bin' function in python works only for integers.
I need a single bit string as in internal representation. I do not want separate bit strings for the number before and after the decimal places joined by a decimal place in between.
EDIT: The question flagged does not explain how to convert binary string to float back.
Copied from this answer and edited per suggestion from Mark Dickinson:
import struct
def float_to_bin(num):
return format(struct.unpack('!I', struct.pack('!f', num))[0], '032b')
def bin_to_float(binary):
return struct.unpack('!f',struct.pack('!I', int(binary, 2)))[0]
print float_to_bin(3.14) yields “01000000010010001111010111000011”.
print bin_to_float("11000000001011010111000010100100") yields “-2.71000003815”.
I was able to create a program that takes bin decimals as string an returns int decimals!
I used a for loop to start from 1 until the len() of the str+1 to use i number to elevate 2 and, then just keep track of the result with result +=:
def binary_poin_to_number(bin1)->float:
#Try out string slicing here, later
result = 0
for i in range(1,len(bin1)+1):
if bin1[i-1] == '1':
result += 2**-i
return result
Iam working in python 3.6
I receive from serial comunication an string '3F8E353F'. This is a float number 1.111. How can I convert this string to a float number?
Thank you
Ah yes. Since this is 32-bits, unpack it into an int first then:
x='3F8E353F'
struct.unpack('f',struct.pack('i',int(x,16)))
On my system this gives:
>>> x='3F8E353F'
>>> struct.unpack('f',struct.pack('i',int(x,16)))
(1.1109999418258667,)
>>>
Very close to the expected value. However, this can give 'backwards' results based on the 'endianness' of bytes in your system. Some systems store their bytes least significant byte first, others most significant byte first. See this reference page for the descriptors to format based on byte order.
I used struct.unpack('f',struct.pack('i',int(x,16))) to convert Hex value to float but for negative value I am getting below error
struct.error: argument out of range
To resolve this I used below code which converts Hex (0xc395aa3d) to float value (-299.33). It works for both positive as well for negative value.
x = 0xc395aa3d
struct.unpack('f', struct.pack('I', int(x,16) ))
Another way is to use bytes.fromhex()
import struct
hexstring = '3F8E353F'
struct.unpack('!f', bytes.fromhex(hexstring))[0]
#answer:1.1109999418258667
Note: The form '!' is available for those poor souls who claim they can’t remember whether network byte order is big-endian or little-endian (from struct docs).
I tried several different approaches, from
def ToByteArray(x):
x = int(x)
return x.to_bytes((x.bit_length() + 7) // 8, byteorder='big')
or diving x by 256 and building a new bytearray in a loop but it just feels slow compared to the conversion of a normal python int or in gmpy2 c++.
Isn't there something like an mpz_export in c++? What is the fastest way to accomplish this?
Edit: The reason I need to convert it to bytes is that hashlib cannot hash mpz. If there is another fast way to get a strong cryptographic (sha256) hash of an mpz, without having to convert it to bytes first, that might help aswell!
I think gmpy2.to_binary() will do what you need. It converts a gmpy2 object to portable byte sequence. It uses mpz_export to convert the underlying mpz_t to a sequence of bytes. A short header containing the gmpy2 type and the length is placed at the beginning of the byte sequence. For the gmpy2.mpz type (and assuming the value is not 0), the header is two bytes long.
>>> gmpy2.to_binary(gmpy2.mpz(123456**7))
b'\x01\x01\x00\x00\x00\x00\x00\xe4\x9f\xcc\xfb\xad\xe5\x1f\xec.T'
For example, input is a=5678. How do you make b='5678'? (b is a String).
Not allowed to use str2num or any casting.
Is it possible to use log10? (I know how to do the reverse action).
[This is how I did the opposite (from string to num):
s = input('Enter a number: ','s');
x = sum(10.^(length(s-'0')-1:-1:0).*(s-'0'));
This looks like homework, so first here are some hints:
log10 may be useful to determine the number of digits.
mod can help to obtain each digit.
From your code for the reverse action: using successive powers of 10, as well as +'0' / -'0' to convert between digits and ASCII codes, may also be of help here.
And here's a possible approach using these hints (hover the mouse to find out):
b = char(mod(floor(a./10.^((ceil(log10(a))-1):-1:0)),10) + '0'):