Python error message io UnsupportedOperation not readable

Question

I made a simple program but It shows the following error when I run it   line1      line1 append  xyz    line1 append  abc   line1 append  mno    file   open  File txt   w   for i in range 3       file write line1 i       file write   n    for line in file      print line  file close     It shows this error message      File  C  Users Sachin Patil fourth py py   line 18  in        for line in file       UnsupportedOperation  not readable

User · Answer

There are few modes to open file  read  write etc     If you want to read from file you should type file   open  File txt   r    if write than file   open  File txt   w    You need to give the right permission regarding your usage   more modes    r  Opens a file for reading only   rb  Opens a file for reading only in binary format  r  Opens a file for both reading and writing   rb  Opens a file for both reading and writing in binary format  w  Opens a file for writing only   you can find more modes in here

User · Answer

This will let you read  write and create the file if it don t exist   f   open  filename txt   a    f   open  filename txt   r      Often used commands   f readline    Read next line f seek 0   Jump to beginning f read 0   Read all file f write  test text    Write  test text  to file f close    Close file

User · Answer

Use a  to open a file for reading  writing as well as create it if it doesn t exist      a  Opens a file for both appending and reading  The file pointer is at   the end of the file if the file exists  The file opens in the append   mode  If the file does not exist  it creates a new file for reading   and writing  -Python file modes   with open   File txt    a    as file      print file readlines        file write  test     Note  opening file in a with block makes sure that the file is properly closed at the block s end  even if an exception is raised on the way  It s equivalent to try-finally  but much shorter

User · Answer

You are opening the file as  quot w quot   which stands for writable  Using  quot w quot  you won t be able to read the file  Use the following instead  file   open  quot File txt quot   quot r quot    Additionally  here are the other options   quot r quot    Opens a file for reading only   quot r  quot   Opens a file for both reading and writing   quot rb quot   Opens a file for reading only in binary format   quot rb  quot  Opens a file for both reading and writing in binary format   quot w quot    Opens a file for writing only   quot a quot    Open for writing   The file is created if it does not exist   quot a  quot   Open for reading and writing   The file is created if it does not exist

[python-3.x] Python error message io.UnsupportedOperation: not readable

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