Alternating between variables each run

Question

I want to use different API keys for data scraping each time my program is run.

For instance, I have the following 2 keys:

apiKey1 = "123abc"
apiKey2 = "345def"

and the following URL:

myUrl = http://myurl.com/key=...

When the program is run, I would like myUrl to be using apiKey1. Once it is run again, I would then like it to use apiKey2 and so forth... i.e:

First Run:

url = "http://myurl.com/key=" + apiKey1

Second Run:

url = "http://myurl.com/key=" + apiKey2

Sorry if this doesn't make sense, but does anyone know a way to do this? I have no idea.

---

EDIT:

To avoid confusion, I've had a look at this answer. But this doesn't answer my query. My target is to cycle between the variables between executions of my script.

Answer 1

I would use a persistent dictionary (it's like a database but more lightweight). That way you can easily store the options and the one to visit next.

There's already a library in the standard library that provides such a persistent dictionary: shelve:

import shelve

filename = 'target.shelve'

def get_next_target():
    with shelve.open(filename) as db:
        if not db:
            # Not created yet, initialize it:
            db['current'] = 0
            db['options'] = ["123abc", "345def"]

        # Get the current option
        nxt = db['options'][db['current']]
        db['current'] = (db['current'] + 1) % len(db['options'])  # increment with wraparound

    return nxt

And each call to get_next_target() will return the next option - no matter if you call it several times in the same execution or once per execution.

The logic could be simplified if you never have more than 2 options:

db['current'] = 0 if db['current'] == 1 else 1

But I thought it might be worthwhile to have a way that can easily handle multiple options.

Answer 2

Here is an example of how you can do it with automatic file creation if no such file exists:

import os
if not os.path.exists('Checker.txt'):
    '''here you check whether the file exists
    if not this bit creates it
    if file exists nothing happens'''
    with open('Checker.txt', 'w') as f:
        #so if the file doesn't exist this will create it
        f.write('0')

myUrl = 'http://myurl.com/key='
apiKeys = ["123abc", "345def"]

with open('Checker.txt', 'r') as f:
    data = int(f.read()) #read the contents of data and turn it into int
    myUrl = myUrl + apiKeys[data] #call the apiKey via index

with open('Checker.txt', 'w') as f:
    #rewriting the file and swapping values
    if data == 1:
        f.write('0')
    else:
        f.write('1')