ZEPPELIN-1287. No need to call print to display output in PythonInterpreter

[zjffdu]

What is this PR for?

It is not necessary to call print to display output in PythonInterpreter. 2 main changes:

• the root cause is the displayhook in bootstrap.py
• also did some code refactoring on PythonInterpreter

What type of PR is it?

[Bug Fix]

Todos

• - Task

What is the Jira issue?

• https://issues.apache.org/jira/browse/ZEPPELIN-1287

How should this be tested?

Verify it manually

Screenshots (if appropriate)

Questions:

• Does the licenses files need update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

[zjffdu]

\cc @bzz @Leemoonsoo ready for review, not sure whether the test fail is relevant. CI is very unstable recently, we might need to fix it asap 😃.

[jongyoul]

Merging import to "*" is not recommended. Could you please expand it?

[Leemoonsoo]

Thanks for the contribution.

Tested and it works great.
Could you rebase and see if it passes CI?

[Leemoonsoo]

Looks like test is not passing

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running org.apache.zeppelin.python.PythonInterpreterTest
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/travis/build/apache/zeppelin/zeppelin-interpreter/target/zeppelin-interpreter-0.7.0-SNAPSHOT.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/travis/build/apache/zeppelin/zeppelin-interpreter/target/lib/slf4j-log4j12-1.7.10.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/travis/.m2/repository/org/slf4j/slf4j-log4j12/1.7.10/slf4j-log4j12-1.7.10.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
log4j:WARN No appenders could be found for logger (org.apache.zeppelin.interpreter.Interpreter).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Tests run: 5, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.629 sec <<< FAILURE! - in org.apache.zeppelin.python.PythonInterpreterTest
testInterpret(org.apache.zeppelin.python.PythonInterpreterTest)  Time elapsed: 0.015 sec  <<< FAILURE!
org.junit.ComparisonFailure: expected:<%text []print a> but was:<%text [>>>]print a>
    at org.junit.Assert.assertEquals(Assert.java:115)
    at org.junit.Assert.assertEquals(Assert.java:144)
    at org.apache.zeppelin.python.PythonInterpreterTest.testInterpret(PythonInterpreterTest.java:161)


Results :

Failed tests: 
  PythonInterpreterTest.testInterpret:161 expected:<%text []print a> but was:<%text [>>>]print a>

Tests run: 5, Failures: 1, Errors: 0, Skipped: 0

@zjffdu Could you take a look?

[Leemoonsoo]

@zjffdu Thanks for the contribution!

LGTM

[Leemoonsoo]

Merge to master if there's no more discussion

[minahlee]

Can we merge this into branch-0.6 too? FYI #1232 is merged to branch-0.6. It will be nice to provide same user experience both in pyspark and python interpreter

[zjffdu]

+1 for merging this into branch-0.6

[Leemoonsoo]

+1 for merging this into branch-0.6