Word for requiring a lot of input

Solution 1:

The term input is not usually used to describe the act of programming, but rather the input required when a program runs. The term data-hungry is usually used to denote a program that requires a lot of data input.

One could adapt this terminology to describe the act of writing a program as being code-hungry, however this is not a standard term. Having said that, I do believe that any programmer reading the sentence :

While Python allows a programmer to write short, concise programs, Java is very code-hungry.

will know exactly what is meant.

TL/DR;

The main reason a programming language like Python requires less code than Java is that Python includes built-in data typing. In Python, even high level data types like lists, sets, tuples, and even arrays require no explicit declaration of type.

Here I have used a standard term - namely higher level. Python is a higher level programming language than Java.

Solution 2:

In this case, "verbose" accurately describes both "using or expressed in," i.e., the experiences of writer and user. Thus, "...Java requires verbosity." will work fine here, or you can use "verbose" in the original sentence because it is clear that you are writing about the programmer's (writer's) perspective.