Python how to read bytes from file and save it

Question

I want to read bytes from a file and then write those bytes to another file  and save that file   How do I do this

User · Answer

with open  input    rb   as input      with open  output    wb   as output          while True              data   input read 1024              if data                        break             output write data    The above will read 1 kilobyte at a time  and write it  You can support incredibly large files this way  as you won t need to read the entire file into memory

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Use the open function to open the file  The open function returns a file object  which you can use the read and write to files   file input   open  input txt    opens a file in reading mode file output   open  output txt    opens a file in writing mode  data   file input read 1024   read 1024 bytes from the input file file output write data   write the data to the output file

User · Answer

Here s how to do it with the basic file operations in Python  This opens one file  reads the data into memory  then opens the second file and writes it out     in file   open  in-file    rb     opening for  r eading as  b inary data   in file read     if you only wanted to read 512 bytes  do  read 512  in file close    out file   open  out-file    wb     open for  w riting as  b inary out file write data  out file close     We can do this more succinctly by using the with keyboard to handle closing the file   with open  in-file    rb   as in file  open  out-file    wb   as out file      out file write in file read      If you don t want to store the entire file in memory  you can transfer it in pieces   piece size   4096   4 KiB  with open  in-file    rb   as in file  open  out-file    wb   as out file      while True          piece   in file read piece size           if piece                    break   end of file          out file write piece

User · Answer

In my examples I use the  b  flag   wb    rb   when opening the files because you said you wanted to read bytes  The  b  flag tells Python not to interpret end-of-line characters which can differ between operating systems   If you are reading text  then omit the  b  and use  w  and  r  respectively   This reads the entire file in one chunk using the  simplest  Python code  The problem with this approach is that you could run out memory when reading a large file   ifile   open input filename  rb   ofile   open output filename   wb   ofile write ifile read    ofile close   ifile close     This example is refined to read 1MB chunks to ensure it works for files of any size without running out of memory   ifile   open input filename  rb   ofile   open output filename   wb   data   ifile read 1024 1024  while data      ofile write data      data   ifile read 1024 1024  ofile close   ifile close     This example is the same as above but leverages using with to create a context  The advantage of this approach is that the file is automatically closed when exiting the context   with open input filename  rb   as ifile      with open output filename   wb   as ofile          data   ifile read 1024 1024          while data              ofile write data              data   ifile read 1024 1024    See the following    Python open    http   docs python org library functions html open Python read    http   docs python org library stdtypes html file read Python write    http   docs python org library stdtypes html file write Dive into Python File Object Tutorial  http   diveintopython net file handling file objects html

[python] Python, how to read bytes from file and save it?

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