Tuesday, March 14, 2023

Detecting External Scripts in a Python Program

 Python is a popular programming language due to its simplicity, ease of use, and versatility. One of the useful tools in Python for debugging is the Python Debugger (PDB), which allows developers to interactively debug their Python code. PDB enables developers to set breakpoints, inspect variables, and step through code to help identify and resolve issues.

However, when debugging a program that imports external Python scripts, it can be challenging to detect these external scripts in PDB. The lack of visibility into external scripts can make debugging more complicated and time-consuming. In this article, we will discuss the importance of detecting external scripts in a Python program when designing a debugging window using PDB.

Figure 1: Using yesterday's post (A Better MVC Example), the sample program 
was able to detect the external python scripts



The Challenge of Debugging External Scripts
Python programs are often composed of multiple files, with each file containing classes, functions, and variables that are used across the program. These files may be located in different directories, which can make it challenging to keep track of their dependencies. External scripts are often imported into a Python program using the import statement or from statement. These external scripts may contain critical functions, classes, and variables that are essential to the program's operation.

When using PDB, the challenge arises when trying to debug a program that imports external scripts. By default, PDB only displays the current frame and does not provide visibility into external scripts. This makes it difficult to see the code in external scripts, set breakpoints, and interact with variables. This limitation can make debugging more challenging, especially if the issue is in an external script.

The Importance of Detecting External Scripts
Detecting external scripts in a Python program when designing a debugging window using PDB is crucial for efficient debugging. By detecting external scripts, developers can ensure that they have visibility into all parts of the program and can effectively debug issues.

One of the ways to detect external scripts in a Python program is to use the Abstract Syntax Tree (AST) module in Python. The AST module is part of the Python standard library and provides a way to parse Python code into an abstract syntax tree. By analyzing the AST of a Python program, developers can identify all the external scripts that the program imports. Once the external scripts are detected, they can be displayed in the debugging window, providing developers with visibility into all parts of the program.

Conclusion
In conclusion, detecting external scripts in a Python program when designing a debugging window using PDB is essential for effective debugging. By detecting external scripts, developers can ensure that they have visibility into all parts of the program and can efficiently debug issues. Python's AST module provides a way to parse Python code into an abstract syntax tree, which can be used to detect external scripts. By displaying external scripts in the debugging window, developers can have visibility into all parts of the program and effectively debug any issues.

I have prepared a simple program for this post and here is the code:


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import ast
import os
import sys
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QFont
from PyQt5.QtWidgets import QApplication, QFileDialog, QHBoxLayout, QLabel, QLineEdit, \
    QMainWindow, QPushButton, QListWidget, QVBoxLayout, QWidget, QListWidgetItem


class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        # Set up the main window layout
        central_widget = QWidget()
        self.setCentralWidget(central_widget)
        main_layout = QVBoxLayout(central_widget)

        # Add a label and QLineEdit to enter the path of the Python script
        input_layout = QHBoxLayout()
        input_label = QLabel('Python script path:')
        input_label.setFixedWidth(120)
        input_layout.addWidget(input_label)
        self.input_edit = QLineEdit()
        input_layout.addWidget(self.input_edit)
        main_layout.addLayout(input_layout)

        # Add a button to open a file dialog to select the Python script
        self.select_button = QPushButton('Select script')
        self.select_button.clicked.connect(self.select_script)
        main_layout.addWidget(self.select_button)

        # Add a label and QListWidget to display the detected Python scripts
        output_label = QLabel('Detected scripts:')
        main_layout.addWidget(output_label)
        self.output_list = QListWidget()
        main_layout.addWidget(self.output_list)

        # Set up the font for the output list
        font = QFont('Courier New', 10)
        self.output_list.setFont(font)

    def select_script(self):
        # Open a file dialog to select the Python script
        options = QFileDialog.Options()
        options |= QFileDialog.DontUseNativeDialog
        filepath, _ = QFileDialog.getOpenFileName(self, 'Select Python script', '', 'Python Files (*.py)', options=options)

        # If a filepath was selected, analyze the script and display the detected scripts
        if filepath:
            self.input_edit.setText(filepath)
            detected_scripts = self.analyze_script(filepath)
            self.display_scripts(detected_scripts)

    def analyze_script(self, filepath):
        # Parse the Python script with AST and extract the imported scripts
        with open(filepath, 'r') as f:
            source = f.read()

        tree = ast.parse(source)
        imported_scripts = set()

        for node in ast.walk(tree):
            if isinstance(node, ast.Import):
                for alias in node.names:
                    if not alias.name.startswith('_'):
                        imported_scripts.add(alias.name)
            elif isinstance(node, ast.ImportFrom):
                if not node.module.startswith('_'):
                    imported_scripts.add(node.module)

        # Find the full path of the imported scripts
        script_dir = os.path.dirname(filepath)
        detected_scripts = set()

        for script in imported_scripts:
            script_path = os.path.join(script_dir, script.replace('.', '/') + '.py')
            if os.path.exists(script_path):
                detected_scripts.add(script_path)

        return detected_scripts

    def display_scripts(self, scripts):
        # Clear the output list and add the detected scripts
        self.output_list.clear()
        for script in scripts:
            item = QListWidgetItem(script)
            item.setTextAlignment(Qt.AlignCenter)
            self.output_list.addItem(item)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MainWindow()
    window.setWindowTitle('Python Script Analyzer')
    window.show()
    sys.exit(app.exec_())
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