Python 3 File Handling

Last modified on: October 20, 2024

<h2>Master Python File Handling: Read, Write, and Manage Files Efficiently</h2>
<p>Learn Python file handling with examples on reading, writing, appending, and deleting files. Understand file modes, binary files, and best practices for managing files in Python.</p>
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<h3>Python File Handling Overview</h3>
<p>File handling in Python allows you to work with files&mdash;reading from and writing to them, modifying content, or managing files systematically. Python provides built-in functions to perform these operations easily and efficiently.</p>
<h4>1. <strong>Opening a File</strong></h4>
<p>The <code>open()</code> function is used to open files in Python. It takes two main parameters: the file name and the mode in which the file should be opened.</p>
<p><strong>Syntax</strong>:</p>
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<pre class="language-python"><code>file = open("filename", "mode")</code></pre>
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<p><strong>Common Modes</strong>:</p>
<ul>
<li><strong><code>'r'</code></strong>: Read (default mode). Opens the file for reading, and if the file does not exist, it raises an error.</li>
<li><strong><code>'w'</code></strong>: Write. Opens the file for writing, creates the file if it doesn't exist, and overwrites the content if it exists.</li>
<li><strong><code>'a'</code></strong>: Append. Opens the file for appending, creates the file if it doesn&rsquo;t exist.</li>
<li><strong><code>'x'</code></strong>: Create. Creates a new file, raises an error if the file already exists.</li>
<li><strong><code>'b'</code></strong>: Binary mode (e.g., <code>'rb'</code> or <code>'wb'</code> for reading or writing in binary).</li>
<li><strong><code>'t'</code></strong>: Text mode (default mode for opening files in text).</li>
</ul>
<p><strong>Example</strong>:</p>
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<pre class="language-python"><code>file = open("example.txt", "r")  # Opens the file in read mode</code></pre>
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<h4>2. <strong>Reading from a File</strong></h4>
<p>Once the file is opened in read mode (<code>'r'</code>), there are multiple ways to read the content:</p>
<ul>
<li>
<p><strong>Read the Entire File</strong>:</p>
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<pre class="language-python"><code>file = open("example.txt", "r")
content = file.read()
print(content)
file.close()</code></pre>
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</li>
<li>
<p><strong>Read Line by Line</strong>:</p>
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<pre class="language-python"><code>file = open("example.txt", "r")
for line in file:
    print(line, end='')  # 'end' prevents adding an extra newline
file.close()</code></pre>
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</li>
<li>
<p><strong>Read Specific Number of Characters</strong>:</p>
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<pre class="language-python"><code>file = open("example.txt", "r")
print(file.read(5))  # Reads the first 5 characters
file.close()</code></pre>
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</li>
</ul>
<h4>3. <strong>Writing to a File</strong></h4>
<p>To write to a file, the file needs to be opened in write mode (<code>'w'</code>) or append mode (<code>'a'</code>):</p>
<ul>
<li>
<p><strong>Writing Data</strong>:</p>
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<pre class="language-python"><code>file = open("example.txt", "w")
file.write("This is an example of writing to a file.\n")
file.write("Another line of text.")
file.close()</code></pre>
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</li>
<li>
<p><strong>Appending Data</strong>:</p>
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<pre class="language-python"><code>file = open("example.txt", "a")
file.write("\nAppending this line to the file.")
file.close()</code></pre>
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</li>
</ul>
<p>When writing, the content of the file is overwritten if the file is opened in write mode. In append mode, the new data is added at the end of the file.</p>
<h4>4. <strong>Closing a File</strong></h4>
<p>Always ensure to close the file after you're done with it to free up system resources. This is done using the <code>close()</code> method:</p>
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<pre class="language-python"><code>file.close()</code></pre>
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<p>Alternatively, you can use a <code>with</code> statement to automatically close the file:</p>
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<pre class="language-python"><code>with open("example.txt", "r") as file:
    content = file.read()
    print(content)
# No need to call file.close()&mdash;it closes automatically.</code></pre>
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<h4>5. <strong>Deleting a File</strong></h4>
<p>Python allows you to delete files using the <code>os</code> module.</p>
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<pre class="language-python"><code>import os
os.remove("example.txt")</code></pre>
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<p>To check if a file exists before deleting:</p>
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<pre class="language-python"><code>if os.path.exists("example.txt"):
    os.remove("example.txt")
else:
    print("The file does not exist.")
</code></pre>
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<h4>6. <strong>File Handling Modes Summary</strong></h4>
<table>
<thead>
<tr>
<th>Mode</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>'r'</code></td>
<td>Opens file for reading (default mode). Error if file does not exist.</td>
</tr>
<tr>
<td><code>'w'</code></td>
<td>Opens file for writing. Creates file if it does not exist; overwrites.</td>
</tr>
<tr>
<td><code>'a'</code></td>
<td>Opens file for appending. Creates file if it does not exist.</td>
</tr>
<tr>
<td><code>'x'</code></td>
<td>Creates a new file. Error if file already exists.</td>
</tr>
<tr>
<td><code>'b'</code></td>
<td>Binary mode (used with <code>'r'</code>, <code>'w'</code>, <code>'a'</code>, or <code>'x'</code> for binary files).</td>
</tr>
<tr>
<td><code>'t'</code></td>
<td>Text mode (default mode).</td>
</tr>
</tbody>
</table>
<h4>7. <strong>File Operations with Binary Files</strong></h4>
<p>Binary files such as images, PDFs, or audio files can also be handled. Simply open the file in binary mode (<code>'rb'</code>, <code>'wb'</code>).</p>
<p><strong>Example of Reading a Binary File</strong>:</p>
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<pre class="language-python"><code>with open("image.jpg", "rb") as file:
    content = file.read()
    print(content)  # This will display binary data</code></pre>
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<p><strong>Example of Writing to a Binary File</strong>:</p>
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<pre class="language-python"><code>with open("image_copy.jpg", "wb") as file:
    file.write(content)</code></pre>
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<h4>8. <strong>Working with Directories</strong></h4>
<p>To work with directories, Python's <code>os</code> module provides useful functions:</p>
<ul>
<li>
<p><strong>Creating a Directory</strong>:</p>
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<pre class="language-python"><code>os.mkdir("new_folder")</code></pre>
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</li>
<li>
<p><strong>Listing Files in a Directory</strong>:</p>
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<pre class="language-python"><code>files = os.listdir()
print(files)</code></pre>
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</li>
<li>
<p><strong>Removing a Directory</strong>:</p>
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<pre class="language-python"><code>os.rmdir("new_folder")</code></pre>
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</li>
</ul>
<h3>Conclusion</h3>
<p>Python's file handling features make it simple to open, read, write, and delete files. Whether working with text files or binary data, Python provides flexible methods to manipulate files efficiently.</p>
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