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File Handling in Python

File handling is an essential aspect of programming, allowing you to interact with files on your system. Python provides built-in functions and libraries to help you work with files effectively. File handling in Python is straightforward and powerful, enabling you to read from, write to, and manipulate files with ease.

 

 

 

1. Opening a File

To open a file in Python, use the open() function. This function returns a file object, which you can use to read from or write to the file.

Syntax:

file_object = open(file_name, mode)
 

Modes:

  • 'r': Read mode (default). Opens a file for reading.
  • 'w': Write mode. Opens a file for writing (creates a new file or truncates an existing file).
  • 'a': Append mode. Opens a file for appending (creates a new file if it doesn't exist).
  • 'b': Binary mode. Used in conjunction with other modes for binary files.
  • 't': Text mode (default). Used in conjunction with other modes for text files.
  • 'x': Exclusive creation mode. Creates a new file, failing if the file already exists.
  • '+': Read and write mode.

Example:

# Open a file for reading
file = open('example.txt', 'r')
# Open a file for writing
file = open('example.txt', 'w')
# Open a file for appending
file = open('example.txt', 'a')
# Open a file for reading in binary mode
file = open('example.txt', 'rb')
# Open a file for writing and reading
file = open('example.txt', 'w+')
 

 

2. Reading a File

There are several ways to read from a file in Python:

2.1 read()

Reads the entire file as a single string.

Example:

file = open('example.txt', 'r')
content = file.read()
print(content)
file.close()
 

2.2 readline()

Reads one line at a time.

Example:

file = open('example.txt', 'r')
line = file.readline()
while line:
   print(line, end='')  # The `end=''` argument avoids adding extra newlines
   line = file.readline()
file.close()

 

2.3 readlines()

Reads all lines and returns them as a list of strings.

Example:

file = open('example.txt', 'r')
lines = file.readlines()
for line in lines:
   print(line, end='')
file.close()
 

 

3. Writing to a File

You can write to a file using the write() and writelines() methods.

3.1 write()

Writes a string to the file.

Example:

file = open('example.txt', 'w')
file.write('Hello, World!\n')
file.write('This is a test.\n')
file.close()

 

3.2 writelines()

Writes a list of strings to the file.

Example:

file = open('example.txt', 'w')
lines = ['Hello, World!\n', 'This is a test.\n']
file.writelines(lines)
file.close()
 

 

4. Appending to a File

Appending data to an existing file can be done using the append mode 'a'.

Example:

file = open('example.txt', 'a')
file.write('Appending this line.\n')
file.close()
 

 

5. Using with Statement

Using the with statement for file handling is a best practice in Python. It ensures that the file is properly closed after its suite finishes, even if an exception is raised.

Example:

# Using `with` statement for reading
with open('example.txt', 'r') as file:
   content = file.read()
   print(content)
# Using `with` statement for writing
with open('example.txt', 'w') as file:
   file.write('Hello, World!\n')
   file.write('This is a test.\n')
# Using `with` statement for appending
with open('example.txt', 'a') as file:
   file.write('Appending this line.\n')
 

 

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