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Python Debugging with PDB

PDB is a debugging tool that comes with Python, allowing code execution line by line, setting breakpoints and viewing variable values. When using it, you can insert importpdb;pdb.set_trace() into the code to set a breakpoint, or debug a script from scratch using python-mpdbexample.py. Commonly used commands include n executing the next line, s enters the function, c continues to execute, l viewing the code, p prints the variables, and q exits debugging. When encountering an exception, you can trace the error message in combination with pdb.post_mortem(). Mastering these techniques can effectively improve debugging efficiency.

Jul 29, 2025 am 01:09 AM

python debug

python httpx async client example

Use httpx.AsyncClient to efficiently initiate asynchronous HTTP requests. 1. Basic GET requests manage clients through asyncwith and use awaitclient.get to initiate non-blocking requests; 2. Combining asyncio.gather to combine with asyncio.gather can significantly improve performance, and the total time is equal to the slowest request; 3. Support custom headers, authentication, base_url and timeout settings; 4. Can send POST requests and carry JSON data; 5. Pay attention to avoid mixing synchronous asynchronous code. Proxy support needs to pay attention to back-end compatibility, which is suitable for crawlers or API aggregation and other scenarios.

Jul 29, 2025 am 01:08 AM

python pandas to_datetime example

pandas.to_datetime() is used to convert strings, lists, Series, etc. to datetime type, 1. Convert a single date string to Timestamp; 2. Convert a date list to DatetimeIndex; 3. Process special formats such as "%d/%m/%Y" through format parameters; 4. Use errors='coerce' to convert invalid values to NaT; 5. Convert a string column to datetime type in DataFrame; 6. Support time data analysis with time and minutes; in addition, it can handle integer format dates or combine multiple columns to generate dates, which is the core of processing time fields in data cleaning

Jul 29, 2025 am 01:04 AM

python operator itemgetter example

operator.itemgetter is used to extract elements by index or key from iterable objects. It is often used in conjunction with functions such as sorted, max, and min. 1. You can sort the tuple list by index, such as sorting by age itemgetter(1) or grade itemgetter(2); 2. Support multi-field sorting, such as itemgetter(1,2) first by age and then by grade; 3. You can process dictionary lists, extract and sort through key names such as 'salary' or 'dept'; 4. You can extract multiple fields with map, such as itemgetter(0,2) to get names and grades. Compared with lambda, it is more concise and efficient, and is suitable for a variety of data processing scenarios.

Jul 29, 2025 am 01:02 AM

java programming

python sleep example

time.sleep() is a function used in Python to pause program execution. It belongs to the time module and is often used to control rhythm and simulate delays. 1. Basic usage: Pause the program for 3 seconds through time.sleep(3) before continuing to execute. 2. Control frequency in the loop: Use time.sleep(2) in the loop to print the current time every 2 seconds. 3. Simulate loading effect: combine flush=True to output points one by one, with 0.5 seconds apart each time to simulate the loading process. 4. Avoid frequent requests: Call time.sleep(1) after each request in the crawler to reduce the frequency of requests and reduce the pressure on the server. 5. Support floating point numbers: you can pass in decimal parameters such as 0.5 to realize millimeters

Jul 29, 2025 am 01:00 AM

python read file example

It is recommended to use with combined encoding='utf-8' to read the text file, which can be read at one time through read(), iterated by line or readlines() respectively; 2. Use the 'w' mode to overwrite the content, and add the content in the 'a' mode; 3. Use the CSV file to obtain the list or csv.DictReader to parse each line in a dictionary form; 4. Use json.load() to load the data when reading the JSON file, use json.dump() to write and set ensure_ascii=False and indent to improve readability; 5. Use os.path.ex to process the file does not exist.

Jul 29, 2025 am 12:39 AM

python pass by reference example

In Python, function argument transfer is "passing object reference", that is, 1. For mutable objects (such as lists and dictionaries), in-situ modifications (such as append, assignment slice) within the function will directly affect the original object; 2. For immutable objects (such as integers, strings), the original object cannot be changed in the function, and reassigning will only create a new object; 3. The parameters pass a copy of the reference. If the variable is rebinded in the function (such as lst=[...]), the connection with the original object will not be affected, and the external variable will not be affected. Therefore, modifying mutable objects affects the original data, while immutable objects and reassignment do not, which explains why the list is visible externally after modification within the function, while integer changes are only locally.

Jul 29, 2025 am 12:31 AM

java programming

python pip install requirements.txt example

txt file is used to list Python project dependencies, and can be installed with one click through pipinstall-rrequirements.txt; 1. Use pipinstall-rrequirements.txt to install dependencies; 2. It is recommended to create and activate the virtual environment first to avoid polluting the global environment; 3. Use piplist or pipshow package name to verify the installation; 4. Use pipfreeze>requirements.txt to generate a dependency list; 5. Development dependencies can be stored separately in requirements-dev.txt; 6. When installation fails, you can use domestic mirror source to accelerate, such as -ihtt

Jul 29, 2025 am 12:24 AM

What is the difference between == and is in Python

In Python, == and is used differently. 1.== Used to compare whether the values of two objects are equal, and is suitable for most scenarios where data content consistency is required; 2.is is used to check whether two variables point to the same object in memory, mainly used for identity recognition, such as checking whether it is None. For example, two lists with the same content return True using ==, but using is to return False. Therefore, the appropriate operator should be selected according to the needs: use == to determine whether the values are the same, and use is to determine whether it is the same object.

Jul 29, 2025 am 12:23 AM

python rich library example

Use fromrichimportprint to output color, bold, and italic text, such as [boldred] error: [/boldred] file does not exist; 2. Print dictionary directly or use pprint to automatically beautify the JSON data structure and highlight the syntax; 3. Create a table with color and alignment through the Table class, suitable for displaying structured information; 4. Use the track function to quickly implement progress bars with progress percentage and remaining time; 5. Integrate RichHandler to logging to beautify log output and highlight the exception stack; 6. Use the Syntax class to highlight code blocks with line numbers in the terminal; 7. Use the Markdown class to parse and beautiful

Jul 29, 2025 am 12:14 AM

python

Building Recommendation Systems with Graph Databases in Python

Graph database is suitable for recommendation systems because it is good at handling complex relationships. Its specific advantages include: 1. Efficient query of multi-level relationships, 2. Support weighted edge and node type tags, and 3. Combined with Python, flexible recommendation logic can be realized. Traditional databases are inefficient in handling multiple relationships such as users and products, social interactions, etc., while graph databases such as Neo4j can quickly mine second-degree and third-degree relationships through graph traversal algorithms, and Python can import data through driver docking and execute Cypher queries to improve development efficiency. When designing a graph model, users and products should be defined as nodes, behaviors should be edges with attributes, and data can be imported using LOADCSV or dynamic insertion. Recommended logic can extract features based on neighbor behavior, path analysis, and graph algorithm, in Python

Jul 29, 2025 am 12:12 AM

Working with CSV Files in Python

Common methods for Python processing CSV files include: 1. Use the csv module to read the file, read it line by line through csv.reader or access it by column name; 2. When writing the file, you can write a list or csv.DictWriter to the dictionary and automatically add the table header; 3. It is recommended to use pandas for complex data operations, which supports reading, writing, cleaning, filtering, etc.; 4. Pay attention to common problems such as encoding, paths, line breaks and large file processing.

Jul 29, 2025 am 12:09 AM

python pyinstaller onefile example

The method of using PyInstaller to package Python scripts into a single executable file is: 1. Write a script such as hello.py; 2. Install PyInstaller: pipinstallpyinstaller; 3. Run pyinstaller-onefilehello.py to generate a single-file executable program; 4. The output file is located in the dist directory and can be run independently; 5. Optional parameters include --windowed hidden console and --icon add icon, complete commands such as pyinstaller-onefile-windowed-icon=logo.ico-name=welcome

Jul 29, 2025 am 12:06 AM

Pack

python tkinter entry widget example

Create an Entry input box and set the width to 25 characters, and use pack() to layout; 2. Get user input content through entry.get(); 3. Read input when clicking the button. If it is not empty, it will display "Hello, input content" on the label, otherwise it will prompt "Input cannot be empty"; 4. Optional functions include Enter to trigger a click event, clear the input box, set the default text and disable the input status; 5. This example fully implements the input, processing and feedback process, and is suitable for basic scenarios such as login forms and search boxes.

Jul 29, 2025 am 12:04 AM

tkinter