File Handling In Python

In Python, a file operation takes place in the following order.

1. Open a file

2. Read or write (perform operation)

3. Close the file

How to open a file?

Python has a built-in function open() to open a file. This function returns a file object, also called a handle, as it is used to read or modify the file accordingly.

f = open("test.txt")    # open file in current directory
f = open("C:/Python33/README.txt")  # specifying full path

f = open("test.txt")      # equivalent to 'r' or 'rt'
f = open("test.txt",'w')  # write in text mode
f = open("img.bmp",'r+b') # read and write in binary mode

How to close a file Using Python?

f = open("test.txt")
# perform file operations
f.close()

How to write to File Using Python?

with open("C:/Users/Shalki/Desktop/python/del.txt",'w') as f:
   f.write("my first file\n")
   f.write("This file\n\n")
   f.write("contains three lines\n")

How to read files in Python?

f = open("C:/Users/Shalki/Desktop/python/del.txt",'r')
print(f.read(4))    # read the first 4 data
'This'

print(f.read(4))    # read the next 4 data
' is '

print(f.read())     # read in the rest till end of file
'my first file\nThis file\ncontains three lines\n'

print(f.read())  # further reading returns empty sting

Tell & Seek

print(f.read(8))
print(f.read(8))
f.tell()    # get the current file position

f.seek(3)   # bring file cursor to initial position
print(f.read(8))
print(f.read())  # read the entire file

Readline

f = open("C:/Users/Shalki/Desktop/python/del.txt",'r')

print(f.readline())

print(f.readline())

print(f.readline())

print(f.readline())