python中的.dat和.txt文件有什么区别？

Question

in this code why he used .dat file and didn't use .txt file known that i tried it using .txt file and it worked perfectly .
and why the access mode in that way also the information is stored as text not in binary.

import pickle

print("Pickling lists.")
variety = ["sweet", "hot", "dill"]
shape = ["whole", "spear", "chip"]
brand = ["Claussen", "Heinz", "Vlassic"]
f = open("pickles1.dat", "wb")
pickle.dump(variety, f)
pickle.dump(shape, f)
pickle.dump(brand, f)
f.close()

Answer 1

the extension doesn't tell the contents.

Program author used .dat so you cannot open it (easily) with a text editor and see or even change the apparent garbage inside (which is partly ASCII, and partly non-ASCII) which would destroy/corrupt the data.

As long as you open the file in binary, any file "type" will work. Opening in text mode can "corrupt" the file in some cases of line-termination conversion (happens a lot on windows)

Note that pickle is not the best choice when you're dumping native python structures such as lists and dictionaries. In that case, you're better off with json format, which requires text mode, and has the nice advantage to be readable and even editable as long as you respect the original structures.