Python Script to read and write text files

Python Script to write myFile.txt:

The best option to writing text file is using "with" keyword. First we will create the file object f and then f.write('string_content\n') will create text file and write the content into text file.

with open('myFile.txt', 'a') as f:
    f.write("This is the test string01\n")

The above piece of code will create a myFile.txt file in the current directory means in the same location where we are keeping the script. You can give any path for the output file.

with open('D:\myFile.txt', 'a') as f:
    f.write("This is the test string01\n")

Once we create file object we can write many strings into the file.

 with open('D:\myFile.txt', 'a') as f:
    f.write("This is the test string01\n")
    f.write("This is the test string02\n")
    f.write("This is the test string02\n")

Python Script to read myFile.txt:

Use open() and create a file object "f" and the f.readline() reads a single line from the file; a newline character (\n) is left at the end of the string.

f=open('myFile.txt', 'r')
f.readline()
   'This is the test string01\n'
f.readline()
   'This is the test string02\n'
f.readline()
   'This is the test string02\n'
f.readline()
   ''

f.readlines() will print all lines of the file as a list.

f=open('myFile.txt', 'r') 
f.readlines()     
 ['This is the test string01\n', 'This is the test string02\n', 'This is the test string02\n']

So finally the best way to read the file line by line is first take all lines into list using f.readlines() and then iterate the list.

f=open('myFile.txt', 'r') 
fList=f.readlines() 
for line in fList:     
 print line 
This is the test string01 
This is the test string02 
This is the test string02 
 

Note : Open method have 2 argument open(filename,mode) , We have different following kind of modes:

• r    : When the file will only be read
• w  : When the file only writing (an existing file with the same name will be erased)
• a   : Opens the file for appending; any data written to the file is automatically added to the end
• r+ : Opens the file for both reading and writing. The mode argument is optional; 'r' will be assumed if it’s omitted.
• On Windows, 'b' appended to the mode opens the file in binary mode, so there are also modes like 'rb', 'wb', and 'r+b'. Python on Windows makes a distinction between text and binary files 

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