File Operations
===============
What is file?
--------------
=> According to the programming requirements, when we want to store the data permanently we need to use "files".

Types of files?
----------------
=> two types of files:
	1) Text files
		==> must be with ".txt" extension
		==> includes: the character data
		Ex: abc.txt
			name:
			designation:
			working location:
	2) Binary files
		==> these are used to store "binary data"	
		=> binary data includes with: images, audio, video information etc.

Opening the file?
------------------
open():
-------
Syntax:
	file-object/file-pointer = open(fileName, mode)
here:
	mode ==> the operation of the file
File modes:
-----------
1) r-mode
----------
	=> read-mode
	=> r-mode we can specify like:
		"r" or 'r'
	=> when we want to open the existing file for reading operation we can use "r" mode.
	=> Here, the file pointer is positioned at the beginning if the file.
	=> If the specified file is not existed, we can get "FileNotFoundError".
	=> r-mode is the default mode.

2) w-mode
---------
	=> write mode
	=> 'w' or "w"
	=> when we want to open the existing file for writing the data we can use "w" mode.
	=> If the specified file existing with some data, then this file will be overridden.
	=> If the specified file is not existed then the file object/file pointer can create the new file with the given name.

3) a-mode
---------
	=> append mode
	=> 'a' or "a"
	=> can use to open the existing file for the append operation.
	=> a-mode never overridden the data when the specified file is existing with some data.
	=> This can create the new file when the specified file is not existed.

4) r+-mode
-----------
	=> read + write
	=> the previous data in the file will not be deleted.
	=> The file object is pointing to the beginning of the file.
	=> 'r+' or "r+"

5) w+-mode
----------
	=> 'w+' or "w+"
	=> write + read
	=> It will override existing data.

6) a+-mode
-----------
	=> 'a+' or "a+"	
	=> append + read
	=> It won't override the data.

7) x-mode
----------
	=> 'x' or "x"
	=> It can always use to create the new file for writing operation.
	=> when we can try to open the existing file it can give "FileExistsError".
	=> exclusive mode

Ex: fp = open('abc.txt', 'r')

Closing the file?
------------------
close():
--------
Syntax:
	file-object.close()

About File Object?
-------------------
=> file object can be created while opening the file in any mode.
=> File object properties:
	1) name
	2) mode
	3) closed
	4) readable()
	5) writable()

Ex:
----
f = open("abc.txt", "w")
print("Name of the file = ",f.name)
print("Mode of the file = ",f.mode)
print("Is file closed? = ",f.closed)
print("Is readable = ",f.readable())
print("Is writable = ", f.writable())

Writing data into the text file
--------------------------------
write():
--------
Syntax:
	file-object.write(string-data)
	(or)
	file-object.write(list-of-lines-of-data)

Ex:
---
f = open("abcd.txt", "w")
f.write("Python is Easy to Learn")
f.write("Python is using in Data science")
f.write("Python is also useful in AI/ML")
list_file_data = ["Rajesh\n", "Rakesh\n", "Neelam\n", "Sonu\n"]
f.write(list_file_data)
f.close()
	
Reading data from the text file
--------------------------------
=> reading the data from the file:
	1) read() => to read the total data of the file
	2) read(n) => to read only the n-characters of the file
	3) readline() => to read only one line
	4) readlines() => to read all lines of a file.

Ex:
----
f = open("abc.txt", "r")
data = f.read()
print(data)
data1 = f.read(20)
print(data1)
line = f.readline()
line1 = f.readline()
print(line)
lines = f.readlines()
print(lines)

With statement
---------------
Ex:
----
with open("abc.txt", "w") as f:
	f.write("Python\n")
	f.write("Java\n")
	f.write(".Net\n")
	print(f.closed) # False
print(f.closed) # True

seek() method
--------------
=> which can be used to move the cursor to the specified position.

Ex:
----
data = "All students are Intelligent"
f = open("abc.txt", "w")
f.write(data)
with open("abc.txt", "r+") as f:
	text = f.read()
	print(text)
	Print("The current position = ",f.tell())
	f.seek(10)
	Print("The current position = ",f.tell())
	f.write("xyzxyz")
	f.seek(0)
	text = f.read()
	print(text)


tell() method
--------------
=> which can be used to know the current position of the cursor or file pointer we can use "tell() function".

Ex:
----
f = open("abc.txt", "r")
print(f.tell())
print(f.read(2))
print(f.tell())
print(f.read(4))
print(f.tell())

Handling of Binary data
------------------------
rb, wb, ab, r+b, w+b, a+b, xb

Handling of csv files
----------------------
csv ==> comma separated values

Writing the data into csv files:
--------------------------------
import csv
with open("emp.csv", "w", newline = '') as f:
	w = csv.writer(f)
	w.writerow("ENO", "ENAME", "ESAL", "EADDR")
	n = int(input("Enter number of employees:")
	for i in range(n):
		eno = input("Enter employee ID:")
		ename = input("Enter employee Name:")
		esal = input("Enter employee salary:")
		eaddr = input("Enter employee address:")
		w.writerow(eno, ename, esal, eaddr)
print("Total Employee data written into csv file successfully")