What's the Difference Between 'R+' and 'A+' When Open File in Python

What's the difference between 'r+' and 'a+' when open file in python?

Python opens files almost in the same way as in C:

• r+ Open for reading and writing. The stream is positioned at the beginning of the file.

• a+ Open for reading and appending (writing at end of file). The file is created if it does not exist. The initial file position for reading is at the beginning of the file, but output is appended to the end of the file (but in some Unix systems regardless of the current seek position).

what is the difference between r and .read() in Python?

The .read() function is for reading data from a file; So the file should be in read mode and the read mode is 'r' that you asked.

So 'r'is Mode for File and .read() is a function for reading data.

Difference between modes a, a+, w, w+, and r+ in built-in open function?

The opening modes are exactly the same as those for the C standard library function fopen().

The BSD fopen manpage defines them as follows:

 The argument mode points to a string beginning with one of the following
 sequences (Additional characters may follow these sequences.):

 ``r''   Open text file for reading.  The stream is positioned at the
         beginning of the file.

 ``r+''  Open for reading and writing.  The stream is positioned at the
         beginning of the file.

 ``w''   Truncate file to zero length or create text file for writing.
         The stream is positioned at the beginning of the file.

 ``w+''  Open for reading and writing.  The file is created if it does not
         exist, otherwise it is truncated.  The stream is positioned at
         the beginning of the file.

 ``a''   Open for writing.  The file is created if it does not exist.  The
         stream is positioned at the end of the file.  Subsequent writes
         to the file will always end up at the then current end of file,
         irrespective of any intervening fseek(3) or similar.

 ``a+''  Open for reading and writing.  The file is created if it does not
         exist.  The stream is positioned at the end of the file.  Subse-
         quent writes to the file will always end up at the then current
         end of file, irrespective of any intervening fseek(3) or similar.

Difference between parsing a text file in r and rb mode

This depends a little bit on what version of Python you're using. In Python 2, Chris Drappier's answer applies.

In Python 3, its a different (and more consistent) story: in text mode ('r'), Python will parse the file according to the text encoding you give it (or, if you don't give one, a platform-dependent default), and read() will give you a str. In binary ('rb') mode, Python does not assume that the file contains things that can reasonably be parsed as characters, and read() gives you a bytes object.

Also, in Python 3, the universal newlines (the translating between '\n' and platform-specific newline conventions so you don't have to care about them) is available for text-mode files on any platform, not just Windows.

What's the difference between opening a file for update and just appending?

The opening modes are exactly the same that C fopen() std library function.

The BSD fopen manpage defines them as follows:

 ``a''   Open for writing.  The file is created if it does not exist.  The
         stream is positioned at the end of the file.  Subsequent writes
         to the file will always end up at the then current end of file,
         irrespective of any intervening fseek(3) or similar.

 ``a+''  Open for reading and writing.  The file is created if it does not
         exist.  The stream is positioned at the end of the file.  Subse-
         quent writes to the file will always end up at the then current
         end of file, irrespective of any intervening fseek(3) or similar.

The only difference between a and a+ is that a+ allows reading of files.

See this post for more info.

What is the difference between rb and r+b modes in file objects

r+ is used for reading, and writing mode. b is for binary.
r+b mode is open the binary file in read or write mode.

You can read more here.

Purpose of including 'r' in the open() function?

Opening and reading files are different operations.

A file is opened as a first step in reading from it or writing to it. By default, the open() call accesses the file in read mode. Specifying 'r' as the second argument is just explicitly doing the same thing. (Specifying 'w' opens the file in write mode.)

Once the file is open, it can be read in one big chunk (such as your code does), a line at a time, a byte at a time or more complex schemes using different read operations.

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