Python Tutorial 18 --- "Writing And Appending To A File"

Python Tutorial 18 ---

"Writing And Appending To A File"

This PROGRAM or TUTORIAL is about "Writing And Appending To A File"

DOC:

We have already discussed how to open and read a file in Python, in the last tutorial. If you haven’t read the blog, please go and see that one first. Now we will discuss how to write or insert text to a file and also how we can simultaneously read and write a file. Now, as we know, there are different modes of opening a file, we will cover three of them in this tutorial.

Note: f is an object for the file. It is not a method or a special character. You will notice me using f.write() or f.read() or f.close(), in further description or tutorial, but you can use character or word of your own choice instead.

MODES

PURPOSE

“w” mode:

 

Here “w” stands for write. After opening or creating a file, a function, f.write() is used to insert text into the file. The text is written inside closed parenthesis surrounded by double quotations. There is a certain limitation to the write mode of the opening file that it overrides the existing data into the file. For a newly created file, it does no harm, but in case of already existing files, the previous data is lost as f.write() overrides it.  

 

“a” mode:

 

“a” symbolizes append mode here. In English, appends mean adding something at the end of an already written document, and the same is the function the mode performs here. Unlike write mode, when we use "a" keyword, it adds more content at the end of the existing content. The same function i.e., f.write() is used to add text to the file in append mode. It is worth noting that append mode will also create a new file if the file with the same name does not exist and can also be used to write in an empty file.

 

“r+” mode:

 

At the beginning of the description, I told you that we would learn reading and writing a file simultaneously. Well, r+ mode is more of a combination of reading and append than read and write. By opening a file in this mode, we can print the existing content on to the screen by printing f.read() function and adding or appending text to it using f.write() function.


A very helpful tip for beginners:

If you are writing in append mode, start your text by putting a blank space or newline character (\n) else the compiler will start the line from the last word or full stop without any blank space because the curser in case of append mode is placed right after the last character. So, it is always considered a good practice to adopt certain habits that could help you in the future, even though they are not much helpful now.

f.close():

f.close() is used to close a file when we are done with it. It is a good practice to close a file after use because whichever mode you opened it for, the file will be locked in for that specific purpose and could not be accessed outside the program, even though the file browser.

CODE:

#Writing And Appending To A File

# f = open("Saswata2.txt", "w") #This is write mode
# f.write("Saswata is learning python") #this will replace the text
# f.close()

#To add text we will use append
# f = open("Saswata2.txt", "a")
# f.write("Saswata is learning python\n")
# f.close()

#To see the number of characters
# f = open("Saswata2.txt", "a") #if we use write (2) instead of append (a)
# it will simply replace the text and show us the number of chars written in the file.
# a = f.write("Saswata is learning python\n")
# print(a)
# f.close()

#Handel read and write both
f = open("Saswata2.txt", "r+")
print(f.read())
f.write("Python is fun")
f.close()

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