Reading and Writing to text files in Python

Python provides built-in functions for creating, writing, and reading files. Two types of files can be handled in Python, normal text files and binary files (written in binary language, 0s, and 1s).

• Text files: In this type of file, Each line of text is terminated with a special character called EOL (End of Line), which is the new line character (‘\n’) in Python by default.
• Binary files: In this type of file, there is no terminator for a line, and the data is stored after converting it into machine-understandable binary language.

This article will focus on opening, closing, reading, and writing data in a text file. Here, we will also see how to get Python output in a text file.

Opening a Text File in Python

It is done using the open() function. No module is required to be imported for this function.

File_object = open(r"File_Name","Access_Mode")

Example: Here, file1 is created as an object for MyFile1 and file2 as object for MyFile2.

# Open function to open the file "MyFile1.txt"
# (same directory) in append mode and
file1 = open("MyFile1.txt","a")

# store its reference in the variable file1
# and "MyFile2.txt" in D:\Text in file2
file2 = open(r"D:\Text\MyFile2.txt","w+")

Also Read: File Mode in Python

Python Read Text File

There are three ways to read txt file in Python:

• Using read()
• Using readline()
• Using readlines()

Reading From a File Using read()

read(): Returns the read bytes in form of a string. Reads n bytes, if no n specified, reads the entire file.

File_object.read([n])

Reading a Text File Using readline()

readline(): Reads a line of the file and returns in form of a string.For specified n, reads at most n bytes. However, does not reads more than one line, even if n exceeds the length of the line.

File_object.readline([n])

Reading a File Using readlines()

readlines(): Reads all the lines and return them as each line a string element in a list.

  File_object.readlines()

Note: ‘\n’ is treated as a special character of two bytes.

In this example, a file named “myfile.txt” is created and opened in write mode ( "w" ). Data is written to the file using write and writelines methods. The file is then reopened in read and append mode ( "r+" ). Various read operations, including read , readline , readlines , and the use of seek , demonstrate different ways to retrieve data from the file. Finally, the file is closed.

file1 = open("myfile.txt", "w")
L = ["This is Delhi \n", "This is Paris \n", "This is London \n"]

# \n is placed to indicate EOL (End of Line)
file1.write("Hello \n")
file1.writelines(L)
file1.close()  # to change file access modes

file1 = open("myfile.txt", "r+")

print("Output of Read function is ")
print(file1.read())
print()

# seek(n) takes the file handle to the nth
# byte from the beginning.
file1.seek(0)

print("Output of Readline function is ")
print(file1.readline())
print()

file1.seek(0)

# To show difference between read and readline
print("Output of Read(9) function is ")
print(file1.read(9))
print()

file1.seek(0)

print("Output of Readline(9) function is ")
print(file1.readline(9))

file1.seek(0)
# readlines function
print("Output of Readlines function is ")
print(file1.readlines())
print()
file1.close()

Output:

Output of Read function is 
Hello 
This is Delhi 
This is Paris 
This is London 
Output of Readline function is 
Hello 
Output of Read(9) function is 
Hello 
Th
Output of Readline(9) function is 
Hello 
Output of Readlines function is 
['Hello \n', 'This is Delhi \n', 'This is Paris \n', 'This is London \n']

Write to Text File in Python

There are two ways to write in a file:

• Using write()
• Using writelines()

Reference: write() VS writelines()

Writing to a Python Text File Using write()

write(): Inserts the string str1 in a single line in the text file.

File_object.write(str1)

file = open("Employees.txt", "w") 

for i in range(3): 
name = input("Enter the name of the employee: ") 
file.write(name) 
file.write("\n") 
	
file.close() 

print("Data is written into the file.") 

Output:

Data is written into the file.

Writing to a Text File Using writelines()

writelines(): For a list of string elements, each string is inserted in the text file.Used to insert multiple strings at a single time.

File_object.writelines(L) for L = [str1, str2, str3]

file1 = open("Employees.txt", "w") 
lst = [] 
for i in range(3): 
	name = input("Enter the name of the employee: ") 
	lst.append(name + '\n') 
	
file1.writelines(lst) 
file1.close() 
print("Data is written into the file.") 

Output:

Data is written into the file.

Appending to a File in Python

In this example, a file named “myfile.txt” is initially opened in write mode ( "w" ) to write lines of text. The file is then reopened in append mode ( "a" ), and “Today” is added to the existing content. The output after appending is displayed using readlines . Subsequently, the file is reopened in write mode, overwriting the content with “Tomorrow”. The final output after writing is displayed using readlines.

file1 = open("myfile.txt", "w")
L = ["This is Delhi \n", "This is Paris \n", "This is London \n"]
file1.writelines(L)
file1.close()

# Append-adds at last
file1 = open("myfile.txt", "a")  # append mode
file1.write("Today \n")
file1.close()

file1 = open("myfile.txt", "r")
print("Output of Readlines after appending")
print(file1.readlines())
print()
file1.close()

# Write-Overwrites
file1 = open("myfile.txt", "w")  # write mode
file1.write("Tomorrow \n")
file1.close()

file1 = open("myfile.txt", "r")
print("Output of Readlines after writing")
print(file1.readlines())
print()
file1.close()

Output:

Output of Readlines after appending
['This is Delhi \n', 'This is Paris \n', 'This is London \n', 'Today \n']
Output of Readlines after writing
['Tomorrow \n']

Related Article: File Objects in Python

Closing a Text File in Python

Python close() function closes the file and frees the memory space acquired by that file. It is used at the time when the file is no longer needed or if it is to be opened in a different file mode. File_object.close()

# Opening and Closing a file "MyFile.txt"
# for object name file1.
file1 = open("MyFile.txt","a")
file1.close()

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• python-file-handling

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