docs: Added new getting started page (#232)

I tried to do the same thing as we did for the JS client
[here](apify/apify-client-js#542) but for
Python.

The goal is to improve onboarding (adaptation) for using our API (in
Python in this case)

<img width="1768" alt="Snímek obrazovky 2024-05-29 v 17 17 17"
src="https://github.com/apify/apify-client-python/assets/45016873/bbb4a7ae-5542-43a5-9ae9-182715cce88c">

---------

Co-authored-by: Vlada Dusek <v.dusek96@gmail.com>

docs/index.md

@@ -0,0 +1,345 @@
+---
+sidebar_label: 'Getting started'
+title: 'Getting started'
+---
+
+# Apify API client for Python
+
+`apify-client` is the official library to access the [Apify REST API](https://docs.apify.com/api/v2) from your Python applications. It provides useful features like automatic retries and convenience functions that improve the experience of using the Apify API. All requests and responses (including errors) are encoded in JSON format with UTF-8 encoding.
+
+## Pre-requisites
+
+`apify-client` requires Python version 3.8 or higher. Python is available for download on the [official website](https://www.python.org/). Check for your current Python version by running:
+
+```bash
+python -V
+```
+
+## Installation
+
+You can install the client from its [PyPI listing](https://pypi.org/project/apify-client/).
+To do that, run:
+
+```bash
+pip install apify-client
+```
+
+## Authentication and initialization
+
+To use the client, you need an [API token](https://docs.apify.com/platform/integrations/api#api-token). You can find your token under [Integrations](https://console.apify.com/account/integrations) tab in Apify Console. Copy the token and initialize the client by providing the token (`MY-APIFY-TOKEN`) as a parameter to the `ApifyClient` constructor.
+
+```python
+# import Apify client
+from apify_client import ApifyClient
+
+# Client initialization with the API token
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+```
+
+:::warning Secure access
+
+The API token is used to authorize your requests to the Apify API. You can be charged for the usage of the underlying services, so do not share your API token with untrusted parties or expose it on the client side of your applications.
+
+:::
+
+## Quick start
+
+One of the most common use cases is starting [Actors](https://docs.apify.com/platform/actors) (serverless programs running in the [Apify cloud](https://docs.apify.com/platform)) and getting results from their [datasets](https://docs.apify.com/platform/storage/dataset) (storage) after they finish the job (usually scraping, automation processes or data processing).
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+
+# Start an Actor and waits for it to finish
+actor_call = apify_client.actor('username/actor-name').call()
+
+# Get a Actor's dataset
+dataset_client = apify_client.dataset(actor_call['defaultDatasetId'])
+
+# Lists items from the Actor's dataset
+dataset_items = dataset_client.list_items().items
+```
+
+### Running Actors
+
+To start an Actor, you can use the [ActorClient](/reference/class/ActorClient) (`client.actor()`) and pass the Actor's ID (e.g. `john-doe/my-cool-actor`) to define which Actor you want to run. The Actor's ID is a combination of the username and the Actor owner’s username. You can run both your own Actors and [Actors from Apify Store](https://docs.apify.com/platform/actors/running/actors-in-store).
+
+#### Passing input to the Actor
+
+To define the Actor's input, you can pass a run input to the [`call()`](/reference/class/ActorClient#call) method. The input can be any JSON object that the Actor expects (respects the Actor's [input schema](https://docs.apify.com/platform/actors/development/actor-definition/input-schema)).The input is used to pass configuration to the Actor, such as URLs to scrape, search terms, or any other data.
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+
+# Define the input for the Actor
+actor_input = {
+    'some': 'input',
+}
+
+# Start an Actor and waits for it to finish
+actor_call = apify_client.actor('username/actor-name').call(run_input=actor_input)
+```
+
+### Getting results from the dataset
+
+To get the results from the dataset, you can use the [DatasetClient](/reference/class/DatasetClient) (`client.dataset()`) and [`list_items()`](/reference/class/DatasetClient#list_items) method. You need to pass the dataset ID to define which dataset you want to access. You can get the dataset ID from the Actor's run dictionary (represented by `defaultDatasetId`).
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+
+# Get dataset
+dataset_client = apify_client.dataset('dataset-id')
+
+# Lists items from the Actor's dataset
+dataset_items = dataset_client.list_items().items
+```
+
+:::note Dataset access
+
+Running an Actor might take time, depending on the Actor's complexity and the amount of data it processes. If you want only to get data and have an immediate response you should access the existing dataset of the finished [Actor run](https://docs.apify.com/platform/actors/running/runs-and-builds#runs).
+
+:::
+
+## Usage concepts
+
+The `ApifyClient` interface follows a generic pattern that applies to all of its components. By calling individual methods of `ApifyClient`, specific clients that target individual API resources are created. There are two types of those clients:
+
+- [`actorClient`](/reference/class/ActorClient): a client for the management of a single resource
+- [`actorCollectionClient`](/reference/class/ActorCollectionClient): a client for the collection of resources
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+
+# Collection clients do not require a parameter
+actor_collection_client = apify_client.actors()
+
+# Create an actor with the name: my-actor
+my_actor = actor_collection_client.create(name='my-actor')
+
+# List all of your actors
+actor_list = actor_collection_client.list().items
+```
+
+:::note Resource identification
+
+The resource ID can be either the `id` of the said resource, or a combination of your `username/resource-name`.
+
+:::
+
+```python
+# Resource clients accept an ID of the resource
+actor_client = apify_client.actor('username/actor-name')
+
+# Fetch the 'username/actor-name' object from the API
+my_actor = actor_client.get()
+
+# Start the run of 'username/actor-name' and return the Run object
+my_actor_run = actor_client.start()
+```
+
+### Nested clients
+
+Sometimes clients return other clients. That's to simplify working with nested collections, such as runs of a given Actor.
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+
+actor_client = apify_client.actor('username/actor-name')
+runs_client = actor_client.runs()
+
+# List the last 10 runs of the Actor
+actor_runs = runs_client.list(limit=10, desc=True).items
+
+# Select the last run of the Actor that finished with a SUCCEEDED status
+last_succeeded_run_client = actor_client.last_run(status='SUCCEEDED')
+
+# Get dataset
+actor_run_dataset_client = last_succeeded_run_client.dataset()
+
+# Fetch items from the run's dataset
+dataset_items = actor_run_dataset_client.list_items().items
+```
+
+The quick access to `dataset` and other storage directly from the run client can be used with the [`last_run()`](/reference/class/ActorClient#last_run) method.
+
+## Features
+
+Based on the endpoint, the client automatically extracts the relevant data
+and returns it in the expected format.
+Date strings are automatically converted to `datetime.datetime` objects.
+For exceptions, we throw an [`ApifyApiError`](/reference/class/ApifyApiError),
+which wraps the plain JSON errors returned by API and enriches them with other context for easier debugging.
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+
+try:
+    # Try to list items from non-existing dataset
+    dataset_client = apify_client.dataset('not-existing-dataset-id')
+    dataset_items = dataset_client.list_items().items
+except Exception as ApifyApiError:
+    # The exception is an instance of ApifyApiError
+    print(ApifyApiError)
+```
+
+### Retries with exponential backoff
+
+Network communication sometimes fails.
+The client will automatically retry requests that failed due to a network error,
+an internal error of the Apify API (HTTP 500+) or rate limit error (HTTP 429).
+By default, it will retry up to 8 times.
+First retry will be attempted after ~500ms, second after ~1000ms and so on.
+You can configure those parameters using the `max_retries` and `min_delay_between_retries_millis` options
+of the [`ApifyClient`](/reference/class/ApifyClient) constructor.
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient(
+    token='MY-APIFY-TOKEN',
+    max_retries=8,
+    min_delay_between_retries_millis=500, # 0.5s
+    timeout_secs=360, # 6 mins
+)
+```
+
+### Support for asynchronous usage
+
+The package offers an asynchronous version of the client,
+[`ApifyClientAsync`](/reference/class/ApifyClientAsync),
+which allows you to work with the Apify API in an asynchronous way, using the standard `async`/`await` syntax [offered by Python](https://docs.python.org/3/library/asyncio-task.html).
+
+For example, to run an actor and asynchronously stream its log while it's running, you can use this snippet:
+
+```python
+from apify_client import ApifyClientAsync
+apify_client_async = ApifyClientAsync('MY-APIFY-TOKEN')
+
+async def main():
+    run = await apify_client_async.actor('my-actor').start()
+
+    async with apify_client_async.run(run['id']).log().stream() as async_log_stream:
+        if async_log_stream:
+            async for line in async_log_stream.aiter_lines():
+                print(line)
+
+asyncio.run(main())
+```
+
+### Logging
+
+The library logs some useful debug information to the `apify_client` logger
+when sending requests to the Apify API.
+To have them printed out to the standard output, you need to add a handler to the logger:
+
+```python
+import logging
+apify_client_logger = logging.getLogger('apify_client')
+apify_client_logger.setLevel(logging.DEBUG)
+apify_client_logger.addHandler(logging.StreamHandler())
+```
+
+The log records have useful properties added with the `extra` argument,
+like `attempt`, `status_code`, `url`, `client_method` and `resource_id`.
+To print those out, you'll need to use a custom log formatter.
+To learn more about log formatters and how to use them,
+please refer to the official Python [documentation on logging](https://docs.python.org/3/howto/logging.html#formatters).
+
+### Convenience functions and options
+
+Some actions can't be performed by the API itself, such as indefinite waiting for an actor run to finish (because of network timeouts).
+The client provides convenient [`call()`](/reference/class/ActorClient#call)
+and [`wait_for_finish()`](/reference/class/ActorClient#wait_for_finish) methods that do that.
+
+[Key-value store](https://docs.apify.com/platform/storage/key-value-store) records can be retrieved as objects, buffers or streams via the respective options,
+dataset items can be fetched as individual objects or serialized data, or iterated asynchronously.
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+
+# Start an Actor and waits for it to finish
+finished_actor_run = apify_client.actor('username/actor-name').call()
+
+# Starts an Actor and waits maximum 60s (1 minute) for the finish 
+actor_run = apify_client.actor('username/actor-name').start(wait_for_finish=60)
+```
+
+### Pagination
+
+Most methods named `list` or `list_something` return a [`ListPage`](/reference/class/ListPage) object,
+containing properties `items`, `total`, `offset`, `count` and `limit`.
+There are some exceptions though, like `list_keys` or `list_head` which paginate differently.
+The results you're looking for are always stored under `items` and you can use the `limit`
+property to get only a subset of results. Other properties can be available depending on the method.
+
+```python
+from apify_client import ApifyClient
+
+apify_client = ApifyClient('MY-APIFY-TOKEN')
+
+# Resource clients accept an ID of the resource
+dataset_client = apify_client.dataset('dataset-id')
+
+# Number of items per page
+limit = 1000
+# Initial offset
+offset = 0
+# List to store all items
+all_items = []
+
+while True:
+    response = dataset_client.list_items(limit=limit, offset=offset)
+    items = response.items
+    total = response.total
+
+    print(f'Fetched {len(items)} items')
+
+    # Merge new items with other already loaded items
+    all_items.extend(items)
+
+    # If there are no more items to fetch, exit the loading
+    if offset + limit >= total:
+        break
+
+    offset += limit
+
+print(f'Overall fetched {len(all_items)} items')
+```
+
+### Streaming resources
+
+Some resources (dataset items, key-value store records and logs)
+support streaming the resource from the Apify API in parts,
+without having to download the whole (potentially huge) resource to memory before processing it.
+
+The methods to stream these resources are
+[`DatasetClient.stream_items()`](/reference/class/DatasetClient#stream_items),
+[`KeyValueStoreClient.stream_record()`](/reference/class/KeyValueStoreClient#stream_record),
+and [`LogClient.stream()`](/reference/class/LogClient#stream).
+
+Instead of the parsed resource, they return a raw, context-managed
+[`httpx.Response`](https://www.python-httpx.org/quickstart/#streaming-responses) object,
+which has to be consumed using the `with` keyword,
+and automatically gets closed once you exit the `with` block, preventing memory leaks and unclosed connections.
+
+For example, to consume an actor run log in a streaming fashion, you can use this snippet:
+
+```python
+with apify_client.run('MY-RUN-ID').log().stream() as log_stream:
+    if log_stream:
+        for line in log_stream.iter_lines():
+            print(line)
+```