Python file object

Here's some examples of reading and writing files in python,  Thought it might be useful for some.


# open a file for writing
outputFile = open("myfile.txt", "w")
outputFile.write("some data")
#writes 3 lines of data
outputFile.writelines("some data 1", "some data 2", "some data 3")
outputFile.close()


# open a file for reading
inputFile = open("myfile", "r")
# read the file up to the end of file and return as string.
mydata = inputFile.read()
# read only 5 bytes of data.
mysubdata = inputFile.read(5)
# read one line of data
mylineofdata = inputFile.readline()
# read 5 lintes of data 
mylinesofdata = inputFile.readlines(5)

 

Here's the python docs on the above function  (trimmed down for just the above examples)
 

class file(object)
 |  file(name[, mode[, buffering]]) -> file object
 |  
 |  Open a file.  The mode can be 'r', 'w' or 'a' for reading (default),
 |  writing or appending.  The file will be created if it doesn't exist
 |  when opened for writing or appending; it will be truncated when
 |  opened for writing.  Add a 'b' to the mode for binary files.
 |  Add a '+' to the mode to allow simultaneous reading and writing.
 |  If the buffering argument is given, 0 means unbuffered, 1 means line
 |  buffered, and larger numbers specify the buffer size.  The preferred way
 |  to open a file is with the builtin open() function.
 |  Add a 'U' to mode to open the file for input with universal newline
 |  support.  Any line ending in the input file will be seen as a '\n'
 |  in Python.  Also, a file so opened gains the attribute 'newlines';
 |  the value for this attribute is one of None (no newline read yet),
 |  '\r', '\n', '\r\n' or a tuple containing all the newline types seen.
 |  
 |  'U' cannot be combined with 'w' or '+' mode.
 
 |  close(...)
 |      close() -> None or (perhaps) an integer.  Close the file.
 |      
 |      Sets data attribute .closed to True.  A closed file cannot be used for
 |      further I/O operations.  close() may be called more than once without
 |      error.  Some kinds of file objects (for example, opened by popen())
 |      may return an exit status upon closing.
 
 |  
 |  read(...)
 |      read([size]) -> read at most size bytes, returned as a string.
 |      
 |      If the size argument is negative or omitted, read until EOF is reached.
 |      Notice that when in non-blocking mode, less data than what was requested
 |      may be returned, even if no size parameter was given.
 |  
 
 |  
 |  readline(...)
 |      readline([size]) -> next line from the file, as a string.
 |      
 |      Retain newline.  A non-negative size argument limits the maximum
 |      number of bytes to return (an incomplete line may be returned then).
 |      Return an empty string at EOF.
 |  
 |  readlines(...)
 |      readlines([size]) -> list of strings, each a line from the file.
 |      
 |      Call readline() repeatedly and return a list of the lines so read.
 |      The optional size argument, if given, is an approximate bound on the
 |      total number of bytes in the lines returned.
 |  
 
 |  write(...)
 |      write(str) -> None.  Write string str to file.
 |      
 |      Note that due to buffering, flush() or close() may be needed before
 |      the file on disk reflects the data written.
 |  
 |  writelines(...)
 |      writelines(sequence_of_strings) -> None.  Write the strings to the file.
 |      
 |      Note that newlines are not added.  The sequence can be any iterable object
 |      producing strings. This is equivalent to calling write() for each string.
 |  
 

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harland's picture

thanks kev, useful

thanks kev, useful

hairygael's picture

Thanks Kevin, this can be

Thanks Kevin, this can be helpful!