Introduction
File handling is an essential part of any programming language. Python provides a simple and efficient way to work with files using built-in functions and methods. You can perform various operations such as reading, writing, appending, and closing files.
Opening a File
The open() function is used to open a file. It requires at least one argument: the file name. Optionally, you can specify the mode in which the file is opened.
Modes
'r': Read (default mode)'w': Write (creates a new file or truncates an existing file)'a': Append (writes data to the end of the file)'b': Binary mode (used with other modes, e.g.,'rb'or'wb')'t': Text mode (default mode, used with other modes, e.g.,'rt'or'wt')'x': Exclusive creation (fails if the file already exists)
Example
# Opening a file in read mode
file = open('example.txt', 'r')
Reading from a File
You can read the contents of a file using the read(), readline(), or readlines() methods.
Example
# Reading the entire file
file = open('example.txt', 'r')
content = file.read()
print(content)
file.close()
Example: Reading Line by Line
# Reading one line at a time
file = open('example.txt', 'r')
line = file.readline()
while line:
print(line, end='') # end='' to avoid adding extra newline
line = file.readline()
file.close()
Example: Reading All Lines into a List
# Reading all lines into a list
file = open('example.txt', 'r')
lines = file.readlines()
for line in lines:
print(line, end='')
file.close()
Writing to a File
You can write to a file using the write() or writelines() methods. When writing to a file, be careful, as it will overwrite any existing content.
Example
# Writing to a file
file = open('example.txt', 'w')
file.write('Hello, world!\n')
file.write('This is a new line.\n')
file.close()
Example: Writing Multiple Lines
# Writing multiple lines to a file
file = open('example.txt', 'w')
lines = ['First line\n', 'Second line\n', 'Third line\n']
file.writelines(lines)
file.close()
Appending to a File
You can append data to a file using the a mode.
Example
# Appending to a file
file = open('example.txt', 'a')
file.write('This line is appended.\n')
file.close()
Using with Statement
The with statement is used for file handling to ensure that the file is properly closed after its suite finishes, even if an exception is raised.
Example
# Using with statement to open and read a file
with open('example.txt', 'r') as file:
content = file.read()
print(content)
Example: Writing Using with Statement
# Using with statement to write to a file
with open('example.txt', 'w') as file:
file.write('Hello, world!\n')
file.write('This is written using with statement.\n')
Working with Binary Files
You can handle binary files by opening the file in binary mode using the b flag.
Example
# Writing to a binary file
with open('example.bin', 'wb') as file:
file.write(b'\x00\x01\x02\x03')
Example: Reading from a Binary File
# Reading from a binary file
with open('example.bin', 'rb') as file:
content = file.read()
print(content) # Output: b'\x00\x01\x02\x03'
Handling File Exceptions
You can handle exceptions that occur during file operations using try-except blocks.
Example
try:
with open('nonexistent_file.txt', 'r') as file:
content = file.read()
except FileNotFoundError:
print("File not found. Please check the file name and try again.")
except Exception as e:
print(f"An error occurred: {e}")
Conclusion
File handling in Python is straightforward and efficient, allowing you to perform various operations such as reading, writing, appending, and closing files. By using the with statement, you can ensure that files are properly closed after their suite finishes, even if an exception is raised. Understanding file handling is essential for many programming tasks, such as data processing and logging.