[Python] defaultdict will not always generate default value

If you didn't assign default data type, then the defaultdict will not generate a default value for a missing key. For this case, we can use get(key) to find the key value and it will not cause error if the key is missing. See the following example.

Using the Stanford parse tree through NLTK

This is a note for using the Stanford parse tree through NLTK.

Environment setup:
http://stackoverflow.com/questions/13883277/stanford-parser-and-nltk

Stanford parse tree module:
http://nlp.stanford.edu/software/lex-parser.shtml#Download

Remember to update the JRE and JDK to the version you need.

Manual for commands:
http://www.nltk.org/api/nltk.parse.html#module-nltk.parse.stanford
http://www.nltk.org/_modules/nltk/tree.html

int is not an object in Java

Type int in Java is not an object. So when we assign a previously created int variable to another newly created int variable, they are not sharing the same memory (they are mutually independent).

Unlike type int, String is an object in Java. When we assign a previously created string assigned to another newly created string, they share the same object.
PS. String is not mutable.

[Python] Counter

The function of "Counter" make it very convenient to count the number of repeated items in two list. See the following example.

[Python] some operations on list

When using a list in Python, we can see the indicator of the items as follows:
x = [0, 1, 2, 3, 4, 5, 6, 7, 8]
x[0],   x[1],   x[2],   x[3],   x[4],   x[5],   x[6],   x[7],   x[8]
x[-0],  x[-8], x[-7],  x[-6],  x[-5], x[-4],  x[-3],  x[-2], x[-1]   <= reverse direction
x[-9]
some usages of list in Python are shown below:

[Python] strip vs. replace

Here are some examples showing the differences between the function of "strip()" and "replace()" in Python.
Be careful! strip() will delete any character in the beginning or end of the word that matches "any" character in the word we put in the strip function. For example, we put "& quot;" as a parameter into strip(), then any character matches ('&', 'q', 'u', 'o', 't', ';') will be deleted. It doesn't have to be exactly the same "string."