# CoinGecko API: Getting Crypto Values This section describes a use case for the CoinGecko API. This use case has been developed by me in Python and the full code is on my [GitHub](https://github.com/federico-trotta/crypto_prices_API). *** ## Prerequisites To use the CoinGecko API you first need to create an account on [their website](https://www.coingecko.com/). Then, you need to create an [API token](https://apiguide.coingecko.com/getting-started/getting-started). The [free plan](https://www.coingecko.com/en/api/pricing) currently allows you to make 10k API calls per month. *** ## Requirements The program uses the `match` statement that, at the time of writing this documentation (November 2023) requires Python 3.10 (or newer versions). As the program calls an API, you also need the `requests` library. You can install it via:\ `$ pip install requests` *** ## Getting started When you use this software you need to launch the `initial.py` file via `$ python3 initial.py`. This will create a file, called `settings.py`, which stores your email and your API token: this way, every time you use this software, you won't need to insert them After that, you can launch the main file via `$ python3 main.py`. Here's how the `initial.py` file works (code reference [here](https://github.com/federico-trotta/crypto_prices_API/blob/main/initial.py)): * The user inserts the email and the API KEY via CLI. * The program checks if the `settings.py` file exists in the settings folder., then * If exists, it warns the user that the file already exists. * If it doesn't exist, it creates it and stores the email and the API KEI inserted by the user. *** ## Structure of the main file After the [first usage](#getting-started), always invoke the main file via `$ python3 main.py`. Here's what it does: 1. It imports the email and the API token from the `settings.py` file. 2. It prints a welcome message reporting the version of the software. 3. It tries to authenticate the user. 4. With a `while` loop, it has a menù that gives the user to choose between three options: 1. Option 1: the user can visualize the price of one crypto in a currency of their choice. Also, the user can choose to store the value of the crypto in a CVS file with the current date. 2. Option 2: the user can visualize the difference between today's and yesterday's price of a crypto. 3. Option 0: it closes the program by breaking the loop. Here we document all the functions used: * [The authentication function](#the-authentication-function) * [The `price` module](#the-price-module) * [The `csv_creation` module](#the-cvs_creation-module) ### The authentication function The authentication function authenticates the user by verifying their email che API token. This is a use case of the `GET/ping` method shown in the [documentation](https://www.coingecko.com/api/documentation). This method has no parameters and returns 200 if the authentication is successful. In Python, we can test it as follows: ```python # Try access by pinging the dedicated URL try: ping_url = "https://api.coingecko.com/api/v3/ping" response = requests.get(url=ping_url, auth=auth) if response.status_code == 200: print(f"\nAccess succesfully granted to the API!") else: print(f"\nAn error occurred while autenticating. Please: try again!") except Exception as e: print(f"\nAn exception occurred:", e) ``` Were the authentication is performed from the email and the API token imported from the `settings.py` file like so (complete code reference [here](https://github.com/federico-trotta/crypto_prices_API/blob/main/main.py)): ```python # Import settings from the settings file email = settings.EMAIL token = settings.API_TOKEN auth = (email + "/token", token) # Create authenticator ``` ### The `price` module [This module](https://github.com/federico-trotta/crypto_prices_API/blob/main/functions/price.py) has two functions that retrieve the price of a currency using the API and make some calculations. The function `visualize_price()` calls the API using the `GET/simple/price` method (for more details on this method, refer to the [API documentation](https://www.coingecko.com/api/documentation)). Here's how this method can be used to show the current price of one crypto with respect to a currency: 
def visualize_price(auth:str)->None:
    """Shows the current price of a crypto with respect to a currency.
    The auth variable is created in the main.py file.
    """
     # User inserts crypto and currency
    crypto = input(f"\nChoose your crypto (for example, write 'bitcoin'):\n")
    currency = input(f"Choose the currency (for example, write 'usd'):\n")
   
    # API call
    url_price = f"https://api.coingecko.com/api/v3/simple/price?ids={crypto}&vs_currencies={currency}"

    response = requests.get(url=url_price, auth=auth)

    # Print current price of a crypto in the selected currency
    try:
        if response.status_code == 200:
            data = response.json()
            print(f"\nThe current price for {crypto} is: {data[crypto][currency]: .1f} {currency}")
        else:
            print(f"An error occurred while getting the price: please, try again!")
     except Exception as e:
        print(f"An exception occurred while trying to get the currency value", e)
For example, suppose we want to know the current price of bitcoin in USD. Here's what you'll see:

The current price of bitcoin in USD.

The function `price_change()` calls the API using the `GET/coins/{id}/market_chart` method (for more details on this method, refer to the [API documentation](https://www.coingecko.com/api/documentation)). Here's how this method can be used to calculate the current price of a crypt with respect to a currency and its yesterday's price. We can also calculate the change in price during the day and print it: ```python def price_change(auth:str)->None: '''Shows the difference of the price of a crypto in a currency with respect to the value it had yesterday. The auth variable is created in the main.py file. ''' # User inserts crypto and currency crypto = input(f"\nChoose your crypto (for example, write 'bitcoin'):\n") currency = input(f"Choose the currency (for example, write 'usd'):\n") # API call url_increment = f"https://api.coingecko.com/api/v3/coins/{crypto}/market_chart?vs_currency={currency}&days=1&interval=daily" response = requests.get(url=url_increment, auth=auth) try: if response.status_code == 200: data = response.json() current_value = data["prices"][1][1] yesterday_value = data["prices"][0][1] change_price = current_value - yesterday_value print(f"\nThe current value of {crypto} is {current_value: .1f} {currency} while yesterday's value was {yesterday_value: .1f} {currency}.\nSo, the price has changed by {change_price: .1f} {currency} from yesterday") else: print(f"An error occurred while getting the price: please, try again!") except Exception as e: print(f"An exception occurred while trying to get the currency value", e) ``` For example, suppose we want to know the price of Ethereum in EUR. We'd get the following:

The price of Ethereum in EUR:

Note that the response to the `GET` call is the following:

The GET response.

This is why the slicing used is: * `current_value = data["prices"][1][1]` * `yesterday_value = data["prices"][0][1]` ### The `cvs_creation` module [This module](https://github.com/federico-trotta/crypto_prices_API/blob/main/functions/csv_creation.py) has two functions: * The function `new_csv()` creates a CSV writing the header, if it doesn't exist. * The function `write_data()` writes the current value of a crypto in a currency on the current date. *** ## Using the main file The main file is built as a menu with two options: * Option 1 writes the current value of a crypto and stores its value in the CVS, if the user wants- * Option 2 prints the difference in the value of a crypto between today and yesterday. Let's show how the software is expected to work:

Expected result.

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