opening text file in 'r' mode and printing the list( ) gives a list of all lines

Question

I recently, by mistake, found out that if I print out the list( filehandle ) in python for a file open in 'r' mode, it print out a list of all lines of the file.

File trial.txt:

12345
67890
abcd

Code:

a = open("trial.txt", 'r')
print( list(a) )

Output:

['12345
', '67890
', 'abcd']

Can anyone explain why this happens?

rasjani · Answer

File implements python interators functions: __next__ & __iter__

When you make a list of out of file handle, these will be called by list and populate it with the data from the file.

opening text file in 'r' mode and printing the list( <filehandle> ) gives a list of all lines

1 Answers