Change the Unity theme to Dark in one command

unity_dark_theme.py

# 1. Change the path to Unity Editors in the path_to_unity variable below.
# 2. Edit the search and replace patterns in case they don't work for your version of Unity.
# 3. Run a command like this: python unity_dark_theme.py 2019.3.3f1
# 4. In case something goes wrong, remove Unity.exe and rename Unity_bak.exe to Unity.exe.

import binascii
import shutil
import sys


if len(sys.argv) != 2:
    sys.exit("Provide a Unity version as an argument.")

unity_version = sys.argv[1]

# Change to the path to Unity Editors you are actually using.
path_to_unity = 'c:/Program Files/Unity Editors/{}/Editor'.format(unity_version)

# Edit the search and replace patterns in case they change in the future versions of Unity.
# You can use this video as a reference https://youtu.be/sF44tnX7JbA
search_pattern  = binascii.unhexlify(b'751533C0EB1390')
replace_pattern = binascii.unhexlify(b'741533C0EB1390')

'''
Read a binary file in chunks of 1KB to avoid RAM overusage.
'''
def read_in_chunks(file_object, chunk_size=1024):
    while True:
        data = file_object.read(chunk_size)
        if not data:
            break
        yield data


# Create a backup of Unity
try:
    shutil.copyfile(path_to_unity+'/Unity.exe', path_to_unity+'/Unity_bak.exe')
except IOError:
    sys.exit("No such path to Unity or this version of Unity is not installed.")

pattern_pos = 0

# Find the position of the sequence in the binary file.
with open(path_to_unity+'/Unity.exe', 'rb') as file:
    for piece in read_in_chunks(file):
        pos = piece.find(b'u\x153\xc0\xeb\x13\x90')
        if pos == -1:
            pattern_pos += 1024
        else:
            pattern_pos += pos
            break

# Replace the sequence at a given position
with open(path_to_unity+'/Unity.exe', 'r+b') as file:
    file.seek(pattern_pos)
    file.write(replace_pattern)

print("Done")