To keep a variable’s value after your Python program closes, write it to a file and load it the next time the program runs. For lists and dictionaries, JSON is a good default: use json.dump() to save and json.load() to restore. For plain text or a single simple value, ordinary file I/O may be enough.
Save and reload a dictionary or list with JSON
JSON is a readable text format that works well for common Python data such as dictionaries, lists, strings, numbers, booleans and nested combinations of those values. The json module is part of Python’s standard library.
import json
settings = {"theme": "dark", "volume": 7}
# Save the value
with open("settings.json", "w", encoding="utf-8") as file:
json.dump(settings, file, indent=2)
# Load it in a later run
with open("settings.json", "r", encoding="utf-8") as file:
settings = json.load(file)
print(settings["theme"]) # darkjson.dump(value, file) writes a value to an open text file; json.load(file) reads it back. The with statement closes the file when the block ends. Use text mode and an encoding such as UTF-8 for JSON files.
Run the save code whenever the value changes and the program should preserve it. On a later run, load the file before using the value. The filename is relative to the program’s current working directory unless you provide a different path. If the file does not exist yet, loading it raises FileNotFoundError; create or save the file first, or handle that case in your program.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
Save a plain text value with file I/O
If the value is already text, you can write and read it directly without JSON:
name = "Ada"
with open("name.txt", "w", encoding="utf-8") as file:
file.write(name)
with open("name.txt", "r", encoding="utf-8") as file:
name = file.read()
print(name) # AdaFor a number, convert it to text when writing and parse it when reading. For example, use str(count) to write an integer and int(file.read()) to restore one. Parsing matters because file.read() returns a string, not the original numeric type.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
Choose a storage method for the data and access pattern
| Need | Good starting point | Trade-off |
|---|---|---|
| Plain text or a small primitive value | Text file I/O | You must parse or convert values when reading numeric types. |
| Lists, dictionaries, settings or portable structured data | JSON | Human-readable and interoperable, but custom objects need explicit conversion. |
| Rich Python object graph, used only in Python and from trusted files | Pickle | Python-specific and binary; unpickling untrusted data can execute code. |
| A persistent mapping accessed by keys | shelve |
Convenient persistence interface backed by DBM-style storage; check its documented restrictions. |
| Relational data or database-style queries | sqlite3 |
More structure than saving one serialized object; choose it when the data or access pattern calls for a database. |
Use pickle only for trusted Python data
Pickle can save a broader range of Python objects than JSON, making it useful when both writing and reading are done in Python and the file is trusted. It uses binary mode:
import pickle
# Save a Python object
with open("state.pkl", "wb") as file:
pickle.dump(state, file)
# Load it only if the file is trusted
with open("state.pkl", "rb") as file:
state = pickle.load(file)Python’s pickle documentation warns: “Only unpickle data you trust.” A malicious or tampered pickle file can execute code when loaded. Do not use pickle for files obtained from an untrusted source.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Know what JSON can and cannot restore
JSON does not directly represent every Python type or arbitrary class instance. If your value contains an unsupported object, convert it into JSON-supported values before saving, then write corresponding conversion logic to reconstruct the object when loading. For ordinary nested dictionaries and lists, the direct dump/load pattern is simpler.
Saving a value this way persists the data, not the live variable or the program’s execution state. On the next run, Python creates a new variable when your code assigns the loaded value to it.
Quick Recap
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
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