seek function

Question

Please excuse my confusion here but I have read the documentation regarding the seek   function in python  after having to use it  and although it helped me I am still a bit confused on the actual meaning of what it does  any explanations are much appreciated  thank you

User · Answer

When you open a file  the system points to the beginning of the file  Any read or write you do will happen from the beginning  A seek   operation moves that pointer to some other part of the file so you can read or write at that place   So  if you want to read the whole file but skip the first 20 bytes  open the file  seek 20  to move to where you want to start reading  then continue with reading the file   Or say you want to read every 10th byte  you could write a loop that does seek 9  1   moves 9 bytes forward relative to the current positions   read 1   reads one byte   repeat

User · Answer

For strings  forget about using WHENCE  use f seek 0  to position at beginning of file and f seek len f  1  to position at the end of file   Use open file   r    to read write anywhere in a file  If you use  a   you ll only be able to write  append  at the end of the file regardless of where you position the cursor

User · Answer

The seek function expect s an offset in bytes    Ascii File Example   So if you have a text file with the following content    simple txt  abc   You can jump 1 byte to skip over the first character as following   fp   open  simple txt    r   fp seek 1  print fp readline    gt  gt  gt  bc   Binary file example gathering width    fp   open  afile png    rb   fp seek 16  print  width   0   format struct unpack   gt i   fp read 4   0   print  height     struct unpack   gt i   fp read 4   0       Note  Once you call read you are changing the position of the   read-head  which act s like seek

User · Answer

Regarding seek   there s not too much to worry about   First of all  it is useful when operating over an open file   It s important to note that its syntax is as follows   fp seek offset  from what    where fp is the file pointer you re working with  offset means how many positions you will move  from what defines your point of reference    0  means your reference point is the beginning of the file 1  means your reference point is the current file position 2  means your reference point is the end of the file   if omitted  from what defaults to 0   Never forget that when managing files  there ll always be a position inside that file where you are currently working on  When just open  that position is the beginning of the file  but as you work with it  you may advance  seek will be useful to you when you need to walk along that open file  just as a path you are traveling into

[python] seek() function?

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