Open files in rt and wt modes

Question

Several times here on SO I ve seen people using rt and wt modes for reading and writing files   For example   with open  input txt    rt   as input file       with open  output txt    wt   as output file                  I don t see the modes documented  but since open   doesn t throw an error - looks like it s pretty much legal to use   What is it for and is there any difference between using wt vs w and  rt vs r

User · Accepted Answer

t refers to the text mode   There is no difference between r and rt or w and wt since text mode is the default   Documented here   Character   Meaning  r      open for reading  default   w      open for writing  truncating the file first  x      open for exclusive creation  failing if the file already exists  a      open for writing  appending to the end of the file if it exists  b      binary mode  t      text mode  default          open a disk file for updating  reading and writing   U      universal newlines mode  deprecated    The default mode is  r   open for reading text  synonym of  rt

User · Answer

The t indicates text mode  meaning that  n characters will be translated to the host OS line endings when writing to a file  and back again when reading  The flag is basically just noise  since text mode is the default   Other than U  those mode flags come directly from the standard C library s fopen   function  a fact that is documented in the sixth paragraph of the python2 documentation for open     As far as I know  t is not and has never been part of the C standard  so although many implementations of the C library accept it anyway  there s no guarantee that they all will  and therefore no guarantee that it will work on every build of python  That explains why the python2 docs didn t list it  and why it generally worked anyway  The python3 docs make it official

User · Answer

The  r  is for reading   w  for writing and  a  is for appending   The  t  represents text mode as apposed to binary mode      Several times here on SO I ve seen people using rt and wt modes for reading and writing files    Edit  Are you sure you saw rt and not rb   These functions generally wrap the fopen function which is described here   http   www cplusplus com reference cstdio fopen   As you can see it mentions the use of b to open the file in binary mode   The document link you provided also makes reference to this b mode   Appending  b  is useful even on systems that don   t treat binary and text files differently  where it serves as documentation

User · Answer

t indicates for text mode  https   docs python org release 3 1 5 library functions html open  on linux  there s no difference between text mode and binary mode  however  in windows  they converts  n to  r n when text mode   http   www cygwin com cygwin-ug-net using-textbinary html

[python] Open files in 'rt' and 'wt' modes

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