File handling in Python

1
(No Transcript)
2
Python handling in Python

• Python also supports file handling and allows use
  rs to handle files, i.e. read and write files, al
  ong with many other file handling options. 
• Python handles files differently as text or binary
  , and this is important. 
• Each line of code contains a sequence of characte
  rs and forms a text file. Each line of a file is t
  erminated by a special character called the EOL o
  r the End of the Line characters, such as the , 
  or newline characters. It ends the current line, a
  nd informs the interpreter that a new line has be
  gun.

3

• Hence, in Python, a file operation takes place in
  the following order 1.Creating a file 2.Read
  or write into a file 3.Updating a
  file 4.Deleting a file
• File handling in python is confined to text file
  and binary file.

4
(No Transcript)
5
Text file

• Text fileModes of text file
• Read mode - r
•  Write Mode - w
•  Append mode - a
• read and write mode - r
• write and read mode - w
•  append and read mode - a

6
Opening and closing of a file

• Syntax for opening a filefile object
  open(file_name , access_mode,
  buffering)file_name - The file_name argument
  is a string value that contains the name of the
  file that you want to access.
• access_mode - The access_mode determines the mode
  in which the file has to be opened, i.e., read,
  write, append, etc. A complete list of possible
  values is given below in the table. This is
  optional parameter and the default file access
  mode is read (r).
• buffering - If the buffering value is set to 0,
  no buffering takes place. If the buffering value
  is 1, line buffering is performed while accessing
  a file. If you specify the buffering value as an
  integer greater than 1, then buffering action is
  performed with the indicated buffer size. If
  negative, the buffer size is the system
  default(default behavior).
• Syntax for Closing a filefileObject.close()

7

•  Read mode - r If you open a file in read mode a
  nd if file exist then it will open the file and pl
  aces the cursor at the begining.If you open a fil
  e in read mode and if file does not exist then it 
  will give you the FileNotFoundError. Only reading
   is allowed, writing into the file is unsupported
   operation.
•  Read and Write mode - rIf you open a file in r
  ead mode and if file exist then it will open the 
  file and places the cursor at the begining.
•  If you open a file in read mode and if file d
  oes not exist then it will give you the FileNotFo
  undError.Reading and writing both are allowed.

8

• Write Mode - wIf you open a file in write mode a
  nd if file exist then it will  open the
  file and places the cursor at the beginning
   of the file after deleting the content of the fi
  le.If you open a file in write mode and if file d
  oes not exist then it will create a file with the
   same name and places the cursor at the beginning
   of the file .Only writing is allowed
•  
•  write and read mode - wIf you open a file in w
  rite mode and if file exist then it will open the
   file and places the cursor at the beginning of th
  e file after deleting the content of the file.If
   you open a file in write mode and if file does no
  t exist then it will create a file with the same 
  name and places the cursor at the beginning of the
   file .Only writing and reading both are allowed

9

•  append - a If you open a file in append mode an
  d if file exist then it will open the file and pl
  aces the cursor at the end of the file.If you open
   a file in append mode and if file does not exist 
  then it will create a file with the same name and
   places the cursor at the beginning of the file.
  Only writing is allowed, reading file the file is 
  unsupported operation, But it will always write t
  he content at the end of the file.
• append and read mode - aIf you open a file in a
  ppend mode and if file exist then it will open the
   file and places the cursor at the end of the file
  .If you open a file in append mode and if file do
  es not exist then it will create a file with the 
  same name and places the cursor at the beginning 
  of the file.Only writing and reading both are all
  owed.

10
Operations on a binary file

• Video files , audio files ,pdfs , images are all
  binary files.
• All the operations work in the similar way as
• Modes in binary file read - rb write - wb 
  append - ab read and write - rb
  write and read - wb append and read - ab

11
Methods to read the data

•  read() - reads the whole content of the file and 
  returns  an string object.
•  read(num of char) - reads the specified no of cha
  racters of the file  and returns an string object
  .
•  readline() - reads one line at a tie and returns 
  a string object.
• readlines() -reads all the line form
  the file and returns list of strings where every 
  trying will be one line

12
Example

• f  open('abc.txt', 'r')out_data  f.readlines()
  print(out_data)print()print(type(out_data))f.cl
  ose()
• O/P'What is Lorem Ipsum?\n', 'Lorem Ipsum is
  simply dummy text of the printing and typesetting
  industry. \n', "\\Lorem Ipsum has been the
  industry's standard dummy text ever since the
  1500s, when an unknown printer took a galley of
  type and scrambled it to make a type specimen
  book. \n", 'It has survived not only five
  centuries, but also the leap into electronic
  typesetting, remaining essentially unchanged.
  \n', 'It was popularised in the 1960s with the
  release of Letraset sheets containing Lorem Ipsum
  passages, and more recently with desktop
  publishing software like Aldus PageMaker
  including versions of Lorem Ipsum.\n', '\n', 'Why
  do we use it?\n', 'It is a long established fact
  that a reader will be distracted by the readable
  content of a page when looking at its layout.
  \n', "The point of using Lorem Ipsum is that it
  has a more-or-less normal distribution of
  letters, as opposed to using 'Content here,
  content here', making it look like readable
  English. Many desktop publishing packages and web
  page editors now use Lorem Ipsum as their default
  model text, and a search for 'lorem ipsum' will
  uncover many web sites still in their infancy.
  \n", 'Various versions have evolved over the
  years, sometimes by accident, sometimes on
  purpose (injected humour and the like).\n', 'If
  you open a file in write mode and if file exist
  then it will open the file and places the cursor
  at the begining fo the file after deleting the
  content of the file.' ltclass 'list'gt

13
Methods to write the data

• write('str') - takes a string as input and writes 
  it into a file
•  writelines(list of string)

14
Seek function

• In Python, seek() function is used to change the
  position of the File Handle to a given specific
  position. File handle is like a cursor, which
  defines from where the data has to be read or
  written in the file.
• Syntax f.seek(offset, from_what), where f is
  file pointer
• ParametersOffset Number of postions to move
  forwardfrom_what It defines point of
  reference.The reference point is selected by the
   from_what argument. It accepts three values
• 0 sets the reference point at the beginning of
  the file
• 1 sets the reference point at the current file
  position
• 2 sets the reference point at the end of the
  file

15
Tell method

• The tell() method returns the current file
  position in a file stream.
• Syntaxfile.tell()
• Examplef open("demofile.txt",
  "r")print(f.readline())print(f.tell())
• O/PHello! Welcome to demofile.txt32

16
Thanks for Watching!!!

• For more follow us on our social media platforms
• Instagram learnbay_datascience
• Facebook learnbay
• LinkedIn Learnbay
• Twitter Learnbay1