Steps to create data file in python

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Steps to create data file in python

1. Opening a file 

Before working with data files in Python, the first thing is to open the file. We can use open(  ) function to do it as:

Syntax:

<file_object> = open(<filename>)

OR

<file_object> = open(<filename> , <mode>)

<file_object> is the file object used to read and write data to a file on disk. File object is used to obtain a reference to the file on disk  and open it for different tasks.

<mode> is the file opening mode used to specify the operation we want to perform on file.

Different Modes to Open file are

‘r’

Read only

[File must exist otherwise I/O error is generated ]

‘w’Write only

  • If the file does not exist, file is created.
  • If file exists, Python removes existing data and writes new data in the file.
‘a’Append

  • If the file does not exist, file is created.
  • If file exists, Python will write new data at end of the file.
‘r+’Read only

  • File must exist otherwise I/O error is generated.
  • Both reading and writing of  data can be done.
‘w+’Write and Read

  • If the file does not exist, file is created.
  • If file exists, Python removes existing data and writes new data in the file.
  • Both reading and writing of  data can be done .
‘a+’Write and Read

  • If the file does not exist, file is created.
  • If file exists, Python will write new data at end of the file.
  • Both reading and writing of  data can be done .
‘rb’

Read only in binary mode

[File must exist otherwise I/O error is generated ]

‘wb’Write only in binary mode

  • If the file does not exist, file is created.
  • If file exists, Python removes existing data and writes new data in the file.
‘ab’Append in binary mode

  • If the file does not exist, file is created.
  • If file exists, Python will write new data at end of the file.

‘rb+’

‘r+b’

Read and Write  in binary mode

  • File must exist otherwise I/O error is generated.
  • Both reading and writing of  data can be done.

‘wb+’

‘w+b’

Write and Read in binary mode

  • If the file does not exist, file is created.
  • If file exists, Python removes existing data and writes new data in the file.
  • Both reading and writing of  data can be done .

‘ab+’

‘a+b’

Write and Read in binary mode

  • If the file does not exist, file is created.
  • If file exists, Python will write new data at end of the file.
  • Both reading and writing of  data can be done .

Opening files in Read Mode

Example 1

file1 = open(“data.txt”)

OR

file1 = open(“data.txt”,  “r”)

Above statements open text file “data.txt”  in read mode  and attaches it to file object file1.

Example 2

file2 = open (“d:\\data.txt”)

OR

file2 = open (“d:\\data.txt”, “r”)

Above statements open text file “data.txt” stored in d: drive in read mode  and attaches it to file object file2.

** We can also use single slash in the path but that may generate error as Python also provides escape sequences like \t, \n, \b etc.

Example 3

file3 = open (“d:\files\data.txt”)

OR

file3 = open (“d:\files\data.txt”, “r”)

Above statements open text file “data.txt” stored in d:\files  folder in read mode  and attaches it to file object file3.

** We can also use single slash in the path but that may generate error as Python also provides escape sequences like \t, \n, \b etc.

2.  Reading or writing data in the file

We can write and read data from data files by using different predefined functions of Python. different functions to read and write data in Python are:

  • write()
  • read()
  • readline()

3.  Closing the file

We need to close file after performing required operations on it. Function fclose( ) can be used to close the file.

Syntax of fclose() function is:

<file_object>.close();

Example:

file1.close()




Lesson tags: create data file in python, Data file Handling in Python
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