How to read multiple images from two different folders one by one using python?

Question

I am new to python and in a learning stage.
I am trying to read multiple images from two different folders in a similar order.
Each folder contains 147 images. In one folder there is thermal image (FLIR1271) and second folder contains visible RGB image (FLIR1272) corresponding to thermal image.
My task is to read and display images one by one from each folder at the same time. The code should be written in such a way that FLIR1271 should be read first thermal image folder and then go to next folder and read it’s corresponding visible image FLIR1272. This process should be applied on rest of the 146 images. I tried something given below:

for i in range(0,10):
thermalimages = [] #list of image filenames
  thermal_dir_path = '/content/Infrared_Thermal_Termination_Images'
  thermaldirFiles = os.listdir(thermal_dir_path) #list of directory files
  thermaldirFiles.sort() #good initial sort but doesnt sort numerically very well
  #*sorted(dirFiles) #sort numerically in ascending order
  for files in thermaldirFiles: 
    if '.jpg' in files:
      thermalimages.append(files)
  print (thermalimages)

  visibleimages = [] #list of image filenames
  visible_dir_path = '/content/Visible_Termination_Images'
  visibledirFiles = os.listdir(visible_dir_path) #list of directory files
  visibledirFiles.sort() #good initial sort but doesnt sort numerically very well
  #*sorted(dirFiles) #sort numerically in ascending order
  for files in visibledirFiles: 
    if '.jpg' in files:
      visibleimages.append(files)
  print (visibleimages)

Unfortunately, it’s giving unexpected output:

[‘FLIR1271.jpg’, ‘FLIR1273.jpg’, ‘FLIR1281.jpg’, ‘FLIR1289.jpg’, ‘FLIR1293.jpg’, ‘FLIR1337.jpg’, ‘FLIR1525.jpg’, ‘FLIR1527.jpg’, ‘FLIR1529.jpg’, ‘FLIR1531.jpg’, ‘FLIR1703.jpg’, ‘FLIR1711.jpg’, ‘FLIR1713.jpg’, ‘FLIR1715.jpg’, ‘FLIR1719.jpg’, ‘FLIR1721.jpg’, ‘FLIR1723.jpg’, ‘FLIR1725.jpg’, ‘FLIR1737.jpg’, ‘FLIR1739.jpg’, ‘FLIR1781.jpg’, ‘FLIR1783.jpg’, ‘FLIR1787.jpg’, ‘FLIR1789.jpg’, ‘FLIR1791.jpg’, ‘FLIR1793.jpg’, ‘FLIR1795.jpg’, ‘FLIR1809.jpg’, ‘FLIR1811.jpg’, ‘FLIR1813.jpg’, ‘FLIR1815.jpg’, ‘FLIR1817.jpg’, ‘FLIR1819.jpg’, ‘FLIR1821.jpg’, ‘FLIR1833.jpg’, ‘FLIR1835.jpg’, ‘FLIR1839.jpg’, ‘FLIR1841.jpg’, ‘FLIR1843.jpg’, ‘FLIR1847.jpg’, ‘FLIR1859.jpg’, ‘FLIR1861.jpg’, ‘FLIR1871.jpg’, ‘FLIR1887.jpg’, ‘FLIR1889.jpg’, ‘FLIR1891.jpg’, ‘FLIR1893.jpg’, ‘FLIR1895.jpg’, ‘FLIR1961.jpg’, ‘FLIR1963.jpg’, ‘FLIR1965.jpg’, ‘FLIR1967.jpg’, ‘FLIR1969.jpg’, ‘FLIR1971.jpg’, ‘FLIR1973.jpg’, ‘FLIR1975.jpg’, ‘FLIR1977.jpg’, ‘FLIR1979.jpg’, ‘FLIR1987.jpg’, ‘FLIR1989.jpg’, ‘FLIR1991.jpg’, ‘FLIR1993.jpg’, ‘FLIR1995.jpg’, ‘FLIR1997.jpg’, ‘FLIR1999.jpg’, ‘FLIR2001.jpg’, ‘FLIR2003.jpg’, ‘FLIR2005.jpg’, ‘FLIR2007.jpg’, ‘FLIR2009.jpg’, ‘FLIR2011.jpg’, ‘FLIR2013.jpg’, ‘FLIR2015.jpg’, ‘FLIR2017.jpg’, ‘FLIR2019.jpg’, ‘FLIR2021.jpg’, ‘FLIR2023.jpg’, ‘FLIR2025.jpg’, ‘FLIR2027.jpg’, ‘FLIR2031.jpg’, ‘FLIR2033.jpg’, ‘FLIR2035.jpg’, ‘FLIR2037.jpg’, ‘FLIR2039.jpg’, ‘FLIR2041.jpg’, ‘FLIR2043.jpg’, ‘FLIR2045.jpg’, ‘FLIR2047.jpg’, ‘FLIR2049.jpg’, ‘FLIR2051.jpg’, ‘FLIR2053.jpg’, ‘FLIR2055.jpg’, ‘FLIR2057.jpg’, ‘FLIR2059.jpg’, ‘FLIR2061.jpg’, ‘FLIR2063.jpg’, ‘FLIR2065.jpg’, ‘FLIR2067.jpg’, ‘FLIR2069.jpg’, ‘FLIR2071.jpg’, ‘FLIR2073.jpg’, ‘FLIR2075.jpg’, ‘FLIR2077.jpg’, ‘FLIR2079.jpg’, ‘FLIR2081.jpg’, ‘FLIR2083.jpg’, ‘FLIR2085.jpg’, ‘FLIR2097.jpg’, ‘FLIR2099.jpg’, ‘FLIR2101.jpg’, ‘FLIR2103.jpg’, ‘FLIR2105.jpg’, ‘FLIR2107.jpg’, ‘FLIR2111.jpg’, ‘FLIR2113.jpg’, ‘FLIR2115.jpg’, ‘FLIR2117.jpg’, ‘FLIR2131.jpg’, ‘FLIR2133.jpg’, ‘FLIR2135.jpg’, ‘FLIR2137.jpg’, ‘FLIR2139.jpg’, ‘FLIR2141.jpg’, ‘FLIR2143.jpg’, ‘FLIR2145.jpg’, ‘FLIR2147.jpg’, ‘FLIR2149.jpg’, ‘FLIR2151.jpg’, ‘FLIR2153.jpg’, ‘FLIR2155.jpg’, ‘FLIR2157.jpg’, ‘FLIR2167.jpg’, ‘FLIR2169.jpg’, ‘FLIR2171.jpg’, ‘FLIR2173.jpg’, ‘FLIR2175.jpg’, ‘FLIR2177.jpg’, ‘FLIR2179.jpg’, ‘FLIR2181.jpg’, ‘FLIR2183.jpg’, ‘FLIR2185.jpg’, ‘FLIR2187.jpg’, ‘FLIR2189.jpg’, ‘FLIR2191.jpg’, ‘FLIR2193.jpg’, ‘FLIR2195.jpg’, ‘FLIR2197.jpg’]

Asked By: Saloni_C

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Answer 1

Although in your case, (you have fixed length strings, the prefix is also the same) you might get the expected output after sorting, it’s better not to compare/sort numbers when they are strings. Always pay attention to how you’re sorting the strings containing numbers. i.e "8" is bigger than "12"

And from your explanation about "one by one from each folder at the same time" you need to zip those lists containing file names and iterate through them like:

thermal_files = [f"FLIR127{i}" for i in range(1, 6, 2)]
thermal_files.sort(key=lambda x: int(x.removeprefix("FLIR")))

RGB_files = [f"FLIR127{i}" for i in range(2, 7, 2)]
RGB_files.sort(key=lambda x: int(x.removeprefix("FLIR")))

print(thermal_files)
print(RGB_files)

for thermal, rgb in zip(thermal_files, RGB_files):
    print(f"Do something with thermal: {thermal}")
    print(f"Do something with RGB: {rgb}")
    print("-----------------------------------")

output:

['FLIR1271', 'FLIR1273', 'FLIR1275']
['FLIR1272', 'FLIR1274', 'FLIR1276']
Do something with thermal: FLIR1271
Do something with RGB: FLIR1272
-----------------------------------
Do something with thermal: FLIR1273
Do something with RGB: FLIR1274
-----------------------------------
Do something with thermal: FLIR1275
Do something with RGB: FLIR1276
-----------------------------------

Note: Don’t count on the order of the returned list from os.listdir():

The list is in arbitrary order.

Note: if '.jpg' in files: is not a correct way to check the file’s extension in general. Use .endswith() instead.

Answered By: S.B

How to read multiple images from two different folders one by one using python?

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