MaxCompute:Examples of using the SDK for Python: MaxCompute resources

In most cases, MaxCompute resources are used in user-defined functions (UDFs) and MapReduce. You can use the following methods to perform basic operations on the resources:

• list_resources: queries all resources in a project.
• exist_resource: checks whether a resource exists.
• delete_resource: deletes a resource. You can also use the Resource object to call the drop method to delete a resource.
• create_resource: creates a resource.
• open_resource: reads a resource.

PyODPS supports two types of resources: file resources and table resources.

• File resources
  File resources include files of the FILE, PY, JAR, and ARCHIVE types.

  Note When you upload a PY file in DataWorks, you must set the resource type to file. For more information, see Python UDF documentation.

  For more information about how to perform operations on file resources by using the SDK for Python, see Manage file resources in this topic.
• Table resources: For more information about how to perform operations on table resources by using the SDK for Python, see Manage table resources in this topic.

You can specify a resource name, file type, and file-like object or string to call the create_resource method to create a file resource.

# Use a file-like object to create a file resource. Files, such as compressed packages, must be read in binary mode.
resource = o.create_resource('test_file_resource', 'file', file_obj=open('/to/path/file', 'rb'))
# Use a string to create a file resource.
resource = o.create_resource('test_py_resource', 'py', file_obj='import this')

You can use one of the following methods to open a resource:

• Call the open method for a file resource to open it.
• Call the open_resource method at the MaxCompute entry point to open a file resource.

The opened object is a file-like object. The opening modes of file resources are similar to the open method predefined in Python. The following example demonstrates the opening modes of file resources:

with resource.open('r') as fp:  # Open a resource in read mode. 
    content = fp.read()  # Read all content. 
    fp.seek(0)  # Return to the beginning of the resource. 
    lines = fp.readlines()  # Read multiple lines. 
    fp.write('Hello World')  # An error is returned. Data cannot be written in read mode. 

with o.open_resource('test_file_resource', mode='r+') as fp:  # Open the file in read/write mode. 
    fp.read()
    fp.tell()  # Locate the current position. 
    fp.seek(10)
    fp.truncate()  # Truncate the file to the specified length. 
    fp.writelines(['Hello\n', 'World\n'])  # Write multiple lines into the file. 
    fp.write('Hello World')
    fp.flush()  # Manually call the method to submit the update to MaxCompute. 

PyODPS supports the following opening modes:

• r: read mode. The file can be opened, but data cannot be written to it.
• w: write mode. Data can be written to the file, but data in the file cannot be read. If a file is opened in write mode, the file content is cleared first.
• a: append mode. Data can be added to the end of the file.
• r+: read/write mode. You can read data from and write data to the file.
• w+: This mode is similar to the r+ mode. The only difference is that the file content is cleared first.
• a+: This mode is similar to the r+ mode. The only difference is that data can be written only to the end of the file.

PyODPS also supports the following binary opening modes for some file resources, such as compressed files:

• rb: binary read mode.
• r+b: binary read/write mode.