How to save a list to a file and read it as a list type?

You can use pickle module for that.This module have two methods,

1. Pickling(dump): Convert Python objects into string representation.
2. Unpickling(load): Retrieving original objects from stored string representstion.

https://docs.python.org/3.3/library/pickle.html

Code:

>>> import pickle>>> l = [1,2,3,4]>>> with open("test.txt", "wb") as fp:   #Pickling...   pickle.dump(l, fp)... >>> with open("test.txt", "rb") as fp:   # Unpickling...   b = pickle.load(fp)... >>> b[1, 2, 3, 4]

Also Json

1. dump/dumps: Serialize
2. load/loads: Deserialize

https://docs.python.org/3/library/json.html

Code:

>>> import json>>> with open("test.txt", "w") as fp:...     json.dump(l, fp)...>>> with open("test.txt", "r") as fp:...     b = json.load(fp)...>>> b[1, 2, 3, 4]

I decided I didn't want to use a pickle because I wanted to be able to open the text file and change its contents easily during testing. Therefore, I did this:

score = [1,2,3,4,5]with open("file.txt", "w") as f:    for s in score:        f.write(str(s) +"\n")

score = []with open("file.txt", "r") as f:  for line in f:    score.append(int(line.strip()))

So the items in the file are read as integers, despite being stored to the file as strings.

Although the accepted answer works, you should really be using python's json module:

import jsonscore=[1,2,3,4,5]with open("file.json", 'w') as f:    # indent=2 is not needed but makes the file human-readable    json.dump(score, f, indent=2) with open("file.json", 'r') as f:    score = json.load(f)print(score)

Advantages:

1. json is a widely adopted and standardized data format, so non-python programs can easily read and understand the json files
2. json files are human-readable
3. Any nested or non-nested list/dictionary structure can be saved to a json file (as long as all the contents are serializable).

Disadvantages:

1. The data is stored in plain-text (ie it's uncompressed), which makes it a slow and bloated option for large amounts of data (ie probably a bad option for storing large numpy arrays, that's what hdf5 is for).
2. The contents of a list/dictionary need to be serializable before you can save it as a json, so while you can save things like strings, ints, and floats, you'll need to write custom serialization and deserialization code to save objects, classes, and functions

Which one should I use?:

• If you want to store something you know you're only ever going to use in the context of a python program, use pickle
• If you need to save data that isn't serializable by default (ie objects), save yourself the trouble and use pickle.
• If you need a platform agnostic solution, use json
• If you need to be able to inspect and edit the data directly, use json

Common use cases of json:

• Configuration files (for example, node.js uses a package.json file to track project details, dependencies, scripts, etc ...)
• Most REST APIs use json to transmit and receive data
• Data that requires a nested list/dictionary structure, or requires variable length lists/dicts
• Can be an alternative to csv, xml or yaml files