How to write files and read files in python

In short

for write: use open(“filepath”, “w”)
for read: use open(“filepath”, “r”)
for closing files: use “with” for auto closing the files (realpython)

Python

# write/read text
with open("/tmp/my_file.txt", "w") as file:
    file.write("Eat more kale")
    
with open("/tmp/my_file.txt", "r") as file:
    content = file.read()

# write/read json
import json

with open("tmp/my_file.json", "w") as file:
    json.dump({"vegatble": "kale", "healthy": True }, file)

with open("tmp/my_file.json", "r") as file:
    data = json.load(file)

How would you optimize saving expensive API calls?

Python

def save_read_expensive_api():
    content = expensive_api()

    dir_path = f"tmp/files"
    file_name = f"sample.txt"
    file_path = os.path.join(dir_path, file_name)
    os.makedirs(dir_path, exist_ok=True)

    with open(file_path, "w") as file:
        print("saving file of length: ", len(content))
        file.write(content)


    # with open(file_path, "r") as file:
    #     print("reading file of length: ", len(content))
    #     content = file.read()

    return content

Explanation

Say you have a function with output you want to save. It could be from:

long running calculations (I’ve been running the nurse scheduling problem)
expensive API calls (LLM providers that charge per token 💵)

Python

content = expensive_call(...)

Step: Create the directory you are saving to. I usually write to the system tmp directory or a project tmp tmp directory and put “tmp” in my gitignore so I don’t accidentally commit.

Python

dir_path = f"/tmp/files"
file_name = f"sample.txt"

# this creates the directories if they dont exist
os.makedirs(dir_path, exist_ok=True)

file_path = os.path.join(dir_path, file_name)

Step: make the call and save the output, commenting out the read

Python

# this writes to the file
content = expensive_call(...)

with open(file_path, "w") as file:
    file.write(content)

# this reads from the file
# with open(file_path, "r") as file:
#     content = file.read()

Step: comment out the call and read the file!

Python

# this writes to the file
# content = expensive_call(...)
#
# with open(file_path, "w") as file:
#    file.write(content)

# this reads from the file
with open(file_path, "r") as file:
    content = file.read()