Python Convert String to Byte

Question

I am trying to do some serial input and output operations, and one of those is to send an 8x8 array to an external device (Arduino). The pySerial library requires that the information that I send be a byte. However, in my python code, the 8x8 matrix is made up of types <class 'str'>. Here's my sending function:

import serial
import Matrix

width = 8
height = 8
portName = 'COM3'

def sendMatrix(matrix):
    try:
        port = serial.Serial(portName, 9600, timeout = 1000000)
        port.setDTR(0)
        print("Opened port: \"%s\"." % (portName))
        receivedByte = port.read()
        print(int(receivedByte))
        if (receivedByte == '1'):
            port.write('1')
        bytesWritten = 0
        for row in range(8):
            for col in range(8):
                value = matrix.getPoint(col, row)
                bytesWritten += port.write(value)//ERROR HERE!
        print(int(port.read()));
        port.close()
        print("Data (%d) sent to port: \"%s\"." % (bytesWritten, portName))
    except:
        print("Unable to open the port \"%s\"." % (portName))


def main():
    matrix = Matrix.Matrix.readFromFile('framefile', 8, 8)
    matrix.print()
    print(type(matrix.getPoint(0, 0)))
    print(matrix.getPoint(1, 1))
    sendMatrix(matrix)

main()

Now, I have a class Matrix, which contains a field map, which is the array in question, and I will include that code here too, but the problem I'm having is that each element in the array is of type str, but I need to convert it to a byte. I can disregard possible loss of data, since in practice, I only use 0's and 1's.

My Matrix Class:

class Matrix(object):

    def __init__(self, width, height):
        self.width = width
        self.height = height
        self.map = [[0 for x in range(width)] for y in range(height)]

    def setPoint(self, x, y, value):
        if ((x >= 0) and (x < self.width) and (y >= 0) and (y < self.height)):
            self.map[y][x] = value

    def getPoint(self, x, y):
        if ((x >= 0) and (x < self.width) and (y >= 0) and (y < self.height)):
            return self.map[y][x]

    def print(self):
        for row in range(self.height):
            for col in range(self.width):
                print(str(self.map[row][col])+" ", end="")
            print()

    def save(self, filename):
        f = open(filename, 'w')
        for row in range(self.height):
            for col in range(self.width):
                f.write(str(self.map[row][col]))
            f.write('\n')
        f.close()

    def toByteArray(self):
        matrixBytes = bytearray(self.width * self.height)
        for row in range(self.height):
            for col in range(self.width):
                matrixBytes.append(int(self.map[row][col]))
        return matrixBytes

    def getMap(self):
        return self.map

    def readFromFile(filename, width, height):
        f = open(filename, 'r')
        lines = list(f)
        matrix = Matrix(width, height)
        f.close()
        for row in range(len(lines)):
            matrix.map[row] = lines[row].strip('\n')
        return matrix

matrix is an object, and it contains a width, height, and a 2 dimensional array inside of that. It's not simply an iterable structure. — Andrew Lalis
– Andrew Lalis, Commented Oct 25, 2016 at 9:19
Sure, but the code for your matrix.toByteArray method looks like it serializes the matrix data correctly into a bytearray, and the built-in bytes function will produce a bytes object from that bytearray. — PM 2Ring
– PM 2Ring, Commented Oct 25, 2016 at 9:21

5 revs user1658543 · Accepted Answer · 2020-05-16 13:31:17Z

18

To transform a unicode string to a byte string in Python do this:

>>> 'foo'.encode('utf_8')
b'foo'

To transform a byte string to a unicode string:

>>> b'foo'.decode('utf_8')
'foo'

See encode and decode in the Standard library.

The available encodings are documented in this table. Commonly used ones are utf_8, utf_8_sig, ascii, latin_1 and cp1252. See UTF-8, BOM, ASCII, Latin-1 and Windows-1252 at Wikipedia.

Helpful for debbugging can be raw_unicode_escape. See this table.

edited May 16, 2020 at 13:31

community wiki

5 revs
user1658543

Sign up to request clarification or add additional context in comments.

Comments

SuperNova · Accepted Answer · 2019-10-02 15:01:40Z

6

in Python 3.x, You can use bytes and str like below.

>>> bytes('foo'.encode())
b'foo'

>>> a = bytes('foo'.encode())
>>> str(a.decode())
'foo'

answered Oct 2, 2019 at 15:01

SuperNova

27.7k7 gold badges98 silver badges70 bronze badges

Collectives™ on Stack Overflow

Python Convert String to Byte

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related