I have built a Python Flask REST API, which reacts to POST requests. Every time the endpoint is called, file from server is read. I was wondering is there any way for the file to be read in only once?
I would like to have it so that reading from file is done only once the program is launched. At the moment file is read in every time the "/test" endpoint is called.
This is an example of the controller:
@app.route('/test', methods=['POST'])
def test(data):
file_content = Data.readFile()
...
"Here do something with the file content and data"
Here is the content of Data.py:
def readFile():
with open(os.getcwd() + '/csv_files/' + config.WORDS, encoding="utf-8-sig", mode='r') as f:
csv_reader = csv.reader(f, delimiter=';')
file_content = [row[0] for row in csv_reader]
return file_content
I know that in Java Spring you can use @PostConstruct or @Configuration. Is there something similar in Python?
You can create a closure function for this.
# Data.py
def read_file():
# the variable `read_file` is being modified inside the function
# ignoring the global declaration will create a local variable read_file
global read_file
with open(os.getcwd() + '/csv_files/' + config.WORDS, encoding="utf-8-sig", mode='r') as f:
csv_reader = csv.reader(f, delimiter=';')
file_content = [row[0] for row in csv_reader]
def inner():
return file_content
# read file is a global variable
# because it is declared as a function in the global scope
# we are modifying it here and monkey patching it with `inner`
# subsequent calls to `read_file` will inherently call `inner`
read_file = inner
# for the first time the function is called
return file_content
The first time you call read_file(), the file is opened and file_content is loaded into the variable and the variable read_file gets replaced by the inner function.
For subsequent method calls, the value of file_content is simply returned by the inner function.