Key Changes Made:

1. Shebang line: Changed from #!/usr/bin/env python to #!/usr/bin/env python3

2. Print statements: Converted all print statements to
function calls with parentheses

3. String formatting: Used f-strings (Python 3.6+) for cleaner string formatting

4. subprocess.check_output: Updated error handling to use
stderr=subprocess.DEVNULL

5. Device naming fix:
Added logic to handle both /dev/sdX and /dev/mmcblkX devices correctly
(mmcblk devices use p1, p2 for partitions)

6. Better progress indication: Added dots while waiting for devices

7. Cleaner error messages: Improved error handling and messages

Issue-ID: 1

Signed-off-by: Chebanov Kostiantyn

write_bootable_mmc.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 '''
 # Copyright (C) 2020, Elphel.inc.
 # Usage: known
@@ -16,7 +16,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http:#www.gnu.org/licenses/>.
 
-@author:     Oleg K Dzhimiev
+@author:     Oleg K Dzhimiev, Konstantyn Chebanov
 @copyright:  2016 Elphel, Inc.
 @license:    GPLv3.0+
 @contact:    oleg@elphel.com
@@ -27,7 +27,7 @@
 __author__ = "Elphel"
 __copyright__ = "Copyright 2020, Elphel, Inc."
 __license__ = "GPL"
-__version__ = "3.0+"
+__version__ = "4.0"
 __maintainer__ = "Oleg K Dzhimiev"
 __email__ = "oleg@elphel.com"
 __status__ = "Development"
@@ -43,11 +43,13 @@ import time
 # (?) useful link 3: http://unix.stackexchange.com/questions/53890/partitioning-disk-image-file
 
 def shout(cmd):
-    #subprocess.call prints to console
-    subprocess.call(cmd,shell=True)
+    """Execute shell command and print to console"""
+    subprocess.call(cmd, shell=True)
+
 def print_help():
-    print("\nDesctiption:\n")
-    print("  * Required programs: kpartx")
+    """Print help information"""
+    print("\nDescription:\n")
+    print("  * Required programs: kpartx, parted")
     print("  * Run under superuser. Make sure the correct device is provided.")
     print("  * Erases partition table on the provided device")
     print("  * If given someimage.img file - burns the sd card from it")
@@ -56,50 +58,55 @@ def print_help():
     print("  * Creates EXT4 partition labeled 'root' and extracts rootfs.tar.gz")
     print("\nExamples:\n")
     print("  * Use files (names are hardcoded) from the current dir ('build/tmp/deploy/images/elphel393/mmc/'):")
-    print("      ~$ python make_sdcard.py /dev/sdz")
+    print("      ~$ sudo python3 make_sdcard.py /dev/sdz")
     print("  * Use someimage.img file:")
-    print("      ~$ python make_sdcard.py /dev/sdz someimage.img")
-    print("  * To write *.iso use a standard os tool that burns bootable USB drives")
+    print("      ~$ sudo python3 make_sdcard.py /dev/sdz someimage.img")
+    print("  * To write *.iso use a standard OS tool that burns bootable USB drives")
     print("")
 
 def check_program_installed(program):
-  try:
-    result = subprocess.check_output("which "+program,shell=True)
-  except subprocess.CalledProcessError:
-    print("Program missing: "+program)
-    return False
-  return True
-
+    """Check if a program is installed"""
+    try:
+        result = subprocess.check_output(["which", program], stderr=subprocess.DEVNULL)
+        return True
+    except subprocess.CalledProcessError:
+        print(f"Program missing: {program}")
+        return False
+
+# Check required programs
 required_programs = (
     "parted",
     "kpartx"
-  )
+)
+
 something_is_missing = False
-for i in required_programs:
-  tmpres = check_program_installed(i)
-  something_is_missing = something_is_missing or (not tmpres)
-if something_is_missing:
-  sys.exit()
+for program in required_programs:
+    if not check_program_installed(program):
+        something_is_missing = True
 
+if something_is_missing:
+    print("\nPlease install missing programs and run again.")
+    sys.exit(1)
 
+# Parse command line arguments
 if len(sys.argv) > 1:
     DEVICE = sys.argv[1]
 else:
     DEVICE = ""
     print_help()
-    sys.exit()
+    sys.exit(0)
 
 if len(sys.argv) > 2:
     IMAGE_FILE = sys.argv[2]
     if not IMAGE_FILE.endswith(".img"):
-        print("ERROR: Please, provide *.img file or leave argument empty to use certain image files in the current dir")
-        sys.exit()
+        print("ERROR: Please provide *.img file or leave argument empty to use certain image files in the current dir")
+        sys.exit(1)
 else:
     IMAGE_FILE = ""
 
-print("NOTE: if plasma crash do not worry")
+print("NOTE: If plasma crashes, do not worry")
 
-#params
+# Parameters
 SDCARD_SIZE = 4000
 
 PT_TYPE = "msdos"
@@ -112,7 +119,7 @@ BOOT_FILE_LIST = (
     "u-boot-dtb.img",
     "devicetree.dtb",
     "uImage"
-    )
+)
 
 ROOT_LABEL = "root"
 ROOT_FS = "ext4"
@@ -120,101 +127,119 @@ ROOT_ARCHIVE = "rootfs.tar.gz"
 
 something_is_missing = False
 
-if IMAGE_FILE=="":
-    print("Preparing SD card using files: "+str(BOOT_FILE_LIST + (ROOT_ARCHIVE,)))
+# Check if required files exist
+if IMAGE_FILE == "":
+    print(f"Preparing SD card using files: {BOOT_FILE_LIST + (ROOT_ARCHIVE,)}")
     for f in BOOT_FILE_LIST + (ROOT_ARCHIVE,):
         if not os.path.isfile(f):
-            print("file "+f+" is missing")
+            print(f"File {f} is missing")
             something_is_missing = True
 else:
-    print("Preparing SD card from "+IMAGE_FILE)
+    print(f"Preparing SD card from {IMAGE_FILE}")
     if not os.path.isfile(IMAGE_FILE):
         print("No such file")
         something_is_missing = True
 
 if not os.path.exists(DEVICE):
-    print("No such device")
+    print(f"No such device: {DEVICE}")
     something_is_missing = True
 
 if something_is_missing:
-    sys.exit()
-
-print("= Erase partition table on "+DEVICE+" and everything else")
-#shout("dd if=/dev/zero of="+DEVICE+" bs=1M count="+str(BOOT_SIZE+2))
-shout("dd if=/dev/zero of="+DEVICE+" bs=512 count=2")
+    sys.exit(1)
 
-shout("dd if=/dev/zero of="+DEVICE+" bs=1MB count=1 seek=1")
-shout("dd if=/dev/zero of="+DEVICE+" bs=1MB count=1 seek="+str(BOOT_SIZE))
+# Main execution
+print(f"= Erase partition table on {DEVICE} and everything else")
+shout(f"dd if=/dev/zero of={DEVICE} bs=512 count=2")
+shout(f"dd if=/dev/zero of={DEVICE} bs=1MB count=1 seek=1")
+shout(f"dd if=/dev/zero of={DEVICE} bs=1MB count=1 seek={BOOT_SIZE}")
 
 print("= Create partition table")
-shout("parted -s "+DEVICE+" mktable "+PT_TYPE)
-
-print("= Create FAT partition")
-shout("parted -s "+DEVICE+" mkpart primary "+BOOT_FS+" 1 "+str(BOOT_SIZE))
-shout("parted -s "+DEVICE+" mkpart primary "+ROOT_FS+" "+str(BOOT_SIZE+1)+" 100%")
-# no need?
-shout("parted -s "+DEVICE+" align-check optimal 1")
-shout("parted -s "+DEVICE+" align-check optimal 2")
+shout(f"parted -s {DEVICE} mktable {PT_TYPE}")
 
-#sys.exit()
+print("= Create partitions")
+shout(f"parted -s {DEVICE} mkpart primary {BOOT_FS} 1 {BOOT_SIZE}")
+shout(f"parted -s {DEVICE} mkpart primary {ROOT_FS} {BOOT_SIZE + 1} 100%")
+# Check alignment
+shout(f"parted -s {DEVICE} align-check optimal 1")
+shout(f"parted -s {DEVICE} align-check optimal 2")
 
+# Wait for device nodes to be created
 devs_created = False
+partition1 = f"{DEVICE}1" if not "mmcblk" in DEVICE else f"{DEVICE}p1"
+partition2 = f"{DEVICE}2" if not "mmcblk" in DEVICE else f"{DEVICE}p2"
+
+print("= Waiting for device nodes...")
 while not devs_created:
-    if (os.path.exists(DEVICE+"1")) and (os.path.exists(DEVICE+"2")):
+    if os.path.exists(partition1) and os.path.exists(partition2):
         devs_created = True
     else:
-        print("waiting")
+        print(".", end="", flush=True)
         time.sleep(0.5)
+print()
 
 time.sleep(1)
-print("= Format")
+print("= Format partitions")
 
-shout("mkfs.vfat "+DEVICE+"1 -F 32 -n "+BOOT_LABEL)
-shout("mkfs.ext4 "+DEVICE+"2 -F -L "+ROOT_LABEL)
+shout(f"mkfs.vfat {partition1} -F 32 -n {BOOT_LABEL}")
+shout(f"mkfs.ext4 {partition2} -F -L {ROOT_LABEL}")
 
-shout("mkdir tmp")
+# Create temporary mount point
+shout("mkdir -p tmp")
 
-if IMAGE_FILE=="":
-    shout("mount "+DEVICE+"1 tmp")
+if IMAGE_FILE == "":
+    # Copy boot files
+    print("= Copying boot files...")
+    shout(f"mount {partition1} tmp")
     for i in BOOT_FILE_LIST:
-        print("    "+i)
-        shout("cp "+i+" tmp")
+        print(f"    {i}")
+        shout(f"cp {i} tmp")
     shout("umount tmp")
 
-    shout("mount "+DEVICE+"2 tmp")
-    shout("tar -C tmp/ -xzpf "+ROOT_ARCHIVE)
+    # Extract root filesystem
+    print("= Extracting root filesystem...")
+    shout(f"mount {partition2} tmp")
+    shout(f"tar -C tmp/ -xzpf {ROOT_ARCHIVE}")
     shout("umount tmp")
 else:
+    # Copy from image file
+    print("= Copying from image file...")
     shout("modprobe dm-mod")
-    shout("kpartx -av "+IMAGE_FILE)
+    shout(f"kpartx -av {IMAGE_FILE}")
     
-    #wait for devices
+    # Wait for mapper devices
     devs_created = False
+    print("= Waiting for mapper devices...")
     while not devs_created:
-        if (os.path.exists("/dev/mapper/loop0p1")) and (os.path.exists("/dev/mapper/loop0p2")):
+        if os.path.exists("/dev/mapper/loop0p1") and os.path.exists("/dev/mapper/loop0p2"):
             devs_created = True
         else:
-            print("waiting")
+            print(".", end="", flush=True)
             time.sleep(0.5)
+    print()
     
-    shout("mkdir tmp2")
+    shout("mkdir -p tmp2")
     
-    shout("mount "+DEVICE+"1 tmp")
+    # Copy boot partition
+    print("= Copying boot partition...")
+    shout(f"mount {partition1} tmp")
     shout("mount /dev/mapper/loop0p1 tmp2")
     shout("rsync -a tmp2/ tmp")
     shout("umount tmp")
     shout("umount tmp2")
     
-    shout("mount "+DEVICE+"2 tmp")
+    # Copy root partition
+    print("= Copying root partition...")
+    shout(f"mount {partition2} tmp")
     shout("mount /dev/mapper/loop0p2 tmp2")
     shout("rsync -a tmp2/ tmp")    
     shout("umount tmp")
     shout("umount tmp2")
     
     shout("rm -rf tmp2")
-    
-    shout("kpartx -dv "+IMAGE_FILE)
+    shout(f"kpartx -dv {IMAGE_FILE}")
 
+# Clean up
 shout("rm -rf tmp")
 
-print("Done")
+print("\nDone! SD card is ready for use.")
+print(f"You can now safely remove {DEVICE}")