Python read() function returns empty string [closed]

Question

If I type this in Python:

open("file","r").read()

sometimes it returns the exact content of the file as a string, some other times it returns an empty string (even if the file is not empty). Can someone explain what does this depend on?

Answer 1

When you reach the end of file (EOF) , the .read method returns '', as there is no more data to read.

>>> f = open('my_file.txt')
>>> f.read() # you read the entire file
'My File has data.'
>>> f.read() # you've reached the end of the file 
''
>>> f.tell() # give my current position at file
17
>>> f.seek(0) # Go back to the starting position
>>> f.read() # and read the file again
'My File has data.'

Doc links: read() tell() seek()

Note: If this happens at the first time you read the file, check that the file is not empty. If it's not try putting file.seek(0) before the read.

Answer 2

From the file.read() method documentation:

An empty string is returned when EOF is encountered immediately.

You have hit the end of the file object, there is no more data to read. Files maintain a 'current position', a pointer into the file data, that starts at 0 and is incremented as you read dada.

See the file.tell() method to read out that position, and the file.seek() method to change it.