[FLINK-14509][python] Improve the README.md in flink-python to prepare for PyPI release.

PyFlink will be released on PyPi from FLINK 1.10.0. This commit adds corresponding document for it.

This closes #9982.

docs/tutorials/python_table_api.md

@@ -32,7 +32,8 @@ to running a Python Table API program.
 ## Setting up a Python Project
 
 Firstly, you can fire up your favorite IDE and create a Python project and then
-you need to install the PyFlink package. Please
+you need to install the PyFlink package. You can install the latest PyFlink from PyPI via 
+this command: `pip install apache-flink`. If you want to build and install PyFlink from source code, please
 see [Build PyFlink]({{ site.baseurl }}/flinkDev/building.html#build-pyflink)
 for more details about this.
 

docs/tutorials/python_table_api.zh.md

@@ -30,8 +30,8 @@ under the License.
 
 ## 创建一个Python Table API项目
 
-首先，你可以使用你最熟悉的IDE，创建一个Python项目。然后，你需要安装PyFlink包，
-请参考[构建PyFlink]({{ site.baseurl }}/zh/flinkDev/building.html#build-pyflink)了解详细信息。
+首先，使用您最熟悉的IDE创建一个Python项目。之后执行命令`pip install apache-flink`从PyPI下载安装PyFlink包。
+如果您想从源码安装，请参考[构建PyFlink]({{ site.baseurl }}/zh/flinkDev/building.html#build-pyflink)了解详细信息。
 
 ## 编写一个Flink Python Table API程序
 

flink-python/README.md

@@ -1,37 +1,28 @@
-# Apache Flink Python API
+# Apache Flink
 
-Apache Flink is an open source stream processing framework with the powerful stream- and batch-processing capabilities.
+Apache Flink is a framework and distributed processing engine for stateful computations over unbounded and bounded data streams. Flink has been designed to run in all common cluster environments, perform computations at in-memory speed and at any scale.
 
 Learn more about Flink at [https://flink.apache.org/](https://flink.apache.org/)
 
-This packaging allows you to write Flink programs in Python, but it is currently a very initial version and will change in future versions.
-
-In this initial version only Table API is supported, you can find the documentation at [https://ci.apache.org/projects/flink/flink-docs-master/dev/table/tableApi.html](https://ci.apache.org/projects/flink/flink-docs-master/dev/table/tableApi.html)
+## Python Packaging
 
-## Installation
+This packaging allows you to write Flink programs in Python, but it is currently a very initial version and will change in future versions.
 
-Currently, we can install PyFlink from Flink source code. Enter the directory where this README.md file is located and install PyFlink on your device by executing 
+In this initial version only Table API is supported, you can find the documentation at [https://ci.apache.org/projects/flink/flink-docs-stable/dev/table/tableApi.html](https://ci.apache.org/projects/flink/flink-docs-stable/dev/table/tableApi.html)
 
-```
-python setup.py install
-```
+The tutorial can be found at [https://ci.apache.org/projects/flink/flink-docs-stable/tutorials/python_table_api.html](https://ci.apache.org/projects/flink/flink-docs-stable/tutorials/python_table_api.html)
 
-## Running test cases 
-
-Currently, we use conda and tox to verify the compatibility of the Flink Python API for multiple versions of Python and will integrate some useful plugins with tox, such as flake8.
-We can enter the directory where this README.md file is located and run test cases by executing
-
-```
-./dev/lint-python.sh
-```
+The auto-generated Python docs can be found at [https://ci.apache.org/projects/flink/flink-docs-stable/api/python/](https://ci.apache.org/projects/flink/flink-docs-stable/api/python/)
 
 ## Python Requirements
 
-PyFlink depends on Py4J (currently version 0.10.8.1) and CloudPickle (currently version 1.2.2).
+Apache Flink Python API depends on Py4J (currently version 0.10.8.1), CloudPickle (currently version 1.2.2), python-dateutil(currently version 2.8.0) and Apache Beam (currently version 2.15.0).
+
+## Development Notices
 
-## Development notices
+### Protobuf Code Generation
 
-Protocol buffer is used in this module and file `flink_fn_execution_pb2.py` is generated from `flink-fn-execution.proto`. Whenever `flink-fn-execution.proto` is updated, please re-generate `flink_fn_execution_pb2.py` by executing
+Protocol buffer is used in file `flink_fn_execution_pb2.py` and the file is generated from `flink-fn-execution.proto`. Whenever `flink-fn-execution.proto` is updated, please re-generate `flink_fn_execution_pb2.py` by executing:
 
 ```
 python pyflink/gen_protos.py
@@ -41,3 +32,12 @@ PyFlink depends on the following libraries to execute the above script:
 1. grpcio-tools (>=1.3.5,<=1.14.2)
 2. setuptools (>=37.0.0)
 3. pip (>=7.1.0)
+
+### Running Test Cases 
+
+Currently, we use conda and tox to verify the compatibility of the Flink Python API for multiple versions of Python and will integrate some useful plugins with tox, such as flake8.
+We can enter the directory where this README.md file is located and run test cases by executing
+
+```
+./dev/lint-python.sh
+```