[HOTFIX] Dynamic form in python interpreter

### What is this PR for?
#2106 rewrote python interpreter. But dynamic form feature is not rewritten correctly.

### What type of PR is it?
Hot Fix

### Todos
* [x] - Bring dynamic form back

### What is the Jira issue?
#2106

### How should this be tested?
run

```
%python
print("Hello "+z.input("name", "sun"))
```

```
%python
print("Hello "+z.select("day", [("1","mon"),
                                ("2","tue"),
                                ("3","wed"),
                                ("4","thurs"),
                                ("5","fri"),
                                ("6","sat"),
                                ("7","sun")]))
```

```
%python
options = [("apple","Apple"), ("banana","Banana"), ("orange","Orange")]
print("Hello "+ " and ".join(z.checkbox("fruit", options, ["apple"])))
```

### Questions:
* Does the licenses files need update? no
* Is there breaking changes for older versions? no
* Does this needs documentation? no

Author: Lee moon soo <moon@apache.org>

Closes #2155 from Leemoonsoo/python_get_interpreter_context and squashes the following commits:

c5e584a [Lee moon soo] fix matplotlib display error on python 3.4
3e6603b [Lee moon soo] correctly handle zeppelin.python property.
5be8db4 [Lee moon soo] Expose a method to get InterpreterOutput, so user can call InterpreterOutput.clear()
a405a93 [Lee moon soo] implement dynamic form

interpreter/lib/python/backend_zinline.py

@@ -18,6 +18,7 @@
 
 from __future__ import print_function
 
+import sys
 import uuid
 import warnings
 import base64
@@ -94,7 +95,10 @@ def get_bytes(self, **kwargs):
         buf = BytesIO()
         self.print_figure(buf, **kwargs)
         fmt = fmt.encode()
-        byte_str = b"data:image/%s;base64," %fmt
+        if sys.version_info >= (3, 4) and sys.version_info < (3, 5):
+            byte_str = bytes("data:image/%s;base64," %fmt, "utf-8")
+        else:
+            byte_str = b"data:image/%s;base64," %fmt
         byte_str += base64.b64encode(buf.getvalue())
 
         # Python3 forces all strings to default to unicode, but for raster image

python/src/main/java/org/apache/zeppelin/python/PythonDockerInterpreter.java

@@ -89,8 +89,9 @@ public InterpreterResult interpret(String st, InterpreterContext context) {
           mountPythonScript +
           mountPy4j +
           "-e PYTHONPATH=\"" + pythonPath + "\" " +
-          image +
-          " python /_zeppelin_tmp/" + pythonScript.getName());
+          image + " " +
+          getPythonInterpreter().getPythonBindPath() + " " +
+          "/_zeppelin_tmp/" + pythonScript.getName());
       restartPythonProcess();
       out.clear();
       return new InterpreterResult(InterpreterResult.Code.SUCCESS, "\"" + image + "\" activated");

python/src/main/java/org/apache/zeppelin/python/PythonInterpreter.java

@@ -395,6 +395,10 @@ public InterpreterResult interpret(String cmd, InterpreterContext contextInterpr
     }
   }
 
+  public InterpreterContext getCurrentInterpreterContext() {
+    return context;
+  }
+
   public void interrupt() throws IOException {
     if (pythonPid > -1) {
       logger.info("Sending SIGINT signal to PID : " + pythonPid);
@@ -440,14 +444,23 @@ public void setPythonCommand(String cmd) {
     pythonCommand = cmd;
   }
 
-  public String getPythonCommand() {
+  private String getPythonCommand() {
     if (pythonCommand == null) {
-      return DEFAULT_ZEPPELIN_PYTHON;
+      return getPythonBindPath();
     } else {
       return pythonCommand;
     }
   }
 
+  public String getPythonBindPath() {
+    String path = getProperty("zeppelin.python");
+    if (path == null) {
+      return DEFAULT_ZEPPELIN_PYTHON;
+    } else {
+      return path;
+    }
+  }
+
   private Job getRunningJob(String paragraphId) {
     Job foundJob = null;
     Collection<Job> jobsRunning = getScheduler().getJobsRunning();

python/src/main/resources/python/zeppelin_python.py

@@ -48,25 +48,41 @@ def flush(self):
 
 
 class PyZeppelinContext(object):
-  """ If py4j is detected, these class will be override
-      with the implementation in bootstrap_input.py
+  """ A context impl that uses Py4j to communicate to JVM
   """
-  errorMsg = "You must install py4j Python module " \
-             "(pip install py4j) to use Zeppelin dynamic forms features"
 
-  def __init__(self):
+  def __init__(self, z):
+    self.z = z
+    self.paramOption = gateway.jvm.org.apache.zeppelin.display.Input.ParamOption
+    self.javaList = gateway.jvm.java.util.ArrayList
     self.max_result = 1000
     self._displayhook = lambda *args: None
     self._setup_matplotlib()
 
+  def getInterpreterContext(self):
+    return self.z.getCurrentInterpreterContext()
+
   def input(self, name, defaultValue=""):
-    print(self.errorMsg)
+    return self.z.getGui().input(name, defaultValue)
 
   def select(self, name, options, defaultValue=""):
-    print(self.errorMsg)
+    javaOptions = gateway.new_array(self.paramOption, len(options))
+    i = 0
+    for tuple in options:
+      javaOptions[i] = self.paramOption(tuple[0], tuple[1])
+      i += 1
+    return self.z.getGui().select(name, defaultValue, javaOptions)
 
   def checkbox(self, name, options, defaultChecked=[]):
-    print(self.errorMsg)
+    javaOptions = gateway.new_array(self.paramOption, len(options))
+    i = 0
+    for tuple in options:
+      javaOptions[i] = self.paramOption(tuple[0], tuple[1])
+      i += 1
+    javaDefaultCheck = self.javaList()
+    for check in defaultChecked:
+      javaDefaultCheck.append(check)
+    return self.z.getGui().checkbox(name, javaDefaultCheck, javaOptions)
 
   def show(self, p, **kwargs):
     if hasattr(p, '__name__') and p.__name__ == "matplotlib.pyplot":
@@ -187,7 +203,8 @@ def handler_stop_signals(sig, frame):
 intp = gateway.entry_point
 intp.onPythonScriptInitialized(os.getpid())
 
-z = PyZeppelinContext()
+java_import(gateway.jvm, "org.apache.zeppelin.display.Input")
+z = PyZeppelinContext(intp)
 z._setup_matplotlib()
 
 output = Logger()

spark/src/main/resources/python/zeppelin_pyspark.py

@@ -83,6 +83,9 @@ def put(self, key, value):
   def get(self, key):
     return self.__getitem__(key)
 
+  def getInterpreterContext(self):
+    return self.z.getInterpreterContext()
+
   def input(self, name, defaultValue=""):
     return self.z.input(name, defaultValue)
 

zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/InterpreterContext.java

@@ -192,4 +192,8 @@ public RemoteWorksController getRemoteWorksController() {
   public void setRemoteWorksController(RemoteWorksController remoteWorksController) {
     this.remoteWorksController = remoteWorksController;
   }
+
+  public InterpreterOutput out() {
+    return out;
+  }
 }