I need to read code from the python file and then determine variable type using c++ program.

b = []
def setVal():
a = “string”
b = [1, 2, 3]
return
a = 3

a: int
b:

COSC4315/COSC6345: Determining Data Types in a Dynamic
Language

1 Introduction

Python is interpreted. Here we will take the other route. You will create a ”compiler” program to determine
or infer the data type of each variable. The input source code will be: Python. This “compiler”-style program
will be developed in C++. The output will be a list of variables with their data types, unless the data type
cannot be determined. This list should be alphabetically sorted.

Your program will use regular expression to recognize identifiers, numbers and strings. Your program
will use a simplified context-free grammar to recognize arithmetic expressions with ’+’. In order to detect
data types you will have to perform a partial evaluation using an attribute grammar to extend the parse tree.
Your program does not have to generate intermediate or object code, but this will be required in a future
homework.

The data types in Python will be: bool, int, str, list, . Notice it is not necessary to treat them as
objects.

2 Input

The input is one source code file. The programs will contain the following statements: assignment with
arithmetic expressions, function calls, if/else and while statements, function definitions with up to 2 argu-
ments (like the HW on artimetic operators). The main arithmetic operators will be the ’+’ and ’*’ operator.
The variables can be numbers, strings or lists. In the case of numbers + means addition, for strings it means
concatenation and for lists union. Notice ’*’ is not available for strings or lists; we will ignore Python’s
string repetition. The if condition will be one comparison (no and/or).

You can assume the program will be syntactically correct: detecting syntax errors will be tackled in a
future assignment. You can assume the input source code has no class definitions, no advanced library calls
(e.g. Pandas), and no recursive functions. You can assume there will be no function calls to convert data
types (casting). You can assume lists will not mix data types.

3 Program and output specification

The main program should be called ”gettype.cpp”.
Your program will be compiled:

g++ gettype.cpp -o ˜/bin/gettype

Call syntax from the OS prompt (rename a.out!):

# if in PATH or ˜/bin
gettype file=program1.py

# default
./gettype file=program1.py

3.1 Input and Output:

You will be given a python program as your input file (program1.py).
Your output should be a list of all variables alphabetically sorted with each variable, a colon and its data

type. Do not include any other information.
Example of output:

a: int
c:
cond: bool
l1: list
s: str

4 Requirements

• You should store all the identifiers in some efficient data structure (search time time O(1) or O(log(n))).
These include variable and function identifiers.

• The arithmetic expressions can have up to 8 operands combining + * () and function calls.

• The input is one .py file and it is self-contained (this file will not import other py files).

• You do not have to evaluate any python statement throughout the program. The goal of the homework
is to determine data types.

• In Python a list can mix data types, but in this homework we will take a stricter approach by displaying
a warning when at least one element in the list has a data type conflict with respect to the other ones.

• If one variable is in an expression then entire result is . Therefore, its data type is
.

• It is acceptable to have one variable instance, overwriting the previous occurrence. That is, you do
not have to create new objects.

• You cannot use an existing Python parser. You have to build your own.

• You should use and explore the Python interpreter to verify correctness of your program (use type()
in python to verify). Keep in mind this homework is asking you to develop a ”stricter interpreter” that
performs more static data type checking than the standard Python interpreter.

• The program is required to detect data type conflicts. The program does not have to evaluate the
Python expressions to produce a result.

• You have to create a ”binding” data structure to track data types; which must be clearly highlighted in
your readme file.

• There will not be ”cast” or type conversion function calls since that would require to track types in
functions.

• The program should not halt when encountering syntax or data type errors in the input source code.

• Optional: For each variable you can store its data type and a list of lines where it was set or changed.

• Your program should write error messages to a log file (and optionally to the screen). Your program
should not crash, halt unexpectedly or produce unhandled exceptions. Consider empty input, zeroes
and inconsistent information. Each exception will be -10.

• Test cases: Your program will be tested with 10 test scripts, going from easy to difficult. If your
program fails an easy test script 10-20 points will be deducted. A medium difficulty test case is 10
points off. Difficult cases with specific input issues or complex algorithmic aspects are worth 5 points.

• You can assume the given python program will be clean and there will be no syntax error. 70% of the
grade for each test case will be to detect errors and 30% of the grade will be for detecting warnings.
Your program must print error where python shows error. You do not have to print all the warnings.

• A program not submitted by the deadline is zero points. A non-working program is worth 10 points.
A program that does some computations correctly, but fails several test cases (especially the easy
ones) is worth 50 points. Only programs that work correctly with most input files that produce correct
results will get a score of 80 or higher. In general, correctness is more important than speed.

• Your program will be initially executed using an automated script. So, make sure you follow the
filename and syntax format given in Section 3.

## a program with comment
l1=[2,3,4]
l2=[“2″,”3″]
a=24
b=”45”
c=a*b #this will give result in python, but for this hw, we will say it is .

a: int
b: int
c: int
d: str
k: bool
m: int
n: str

a: int
b: int

a = 3
b = 2
def setVal():
a = “string”
return
b = b + 1

a=4
b=5
c=”str”

x=20
y=40
z=x+y
w=20+40+80
s1=”str1″
s2=s1+w

a=50
b=45
if a>50: #you donot have to evaluate it
c=30
else:
d=”40″ #output will contain both c and d as we are not evaluatiing python code, just getting all the variable types
m=c+100*45
n=d+”coogs”
k=a>b

def f1(a,b):
return a+b
x=f1(2,3)
y=f1(“str1″,”str2″)
z=f1(2,”3”)

k1: str
k2: str
k3:
k4: str
l1: list
l2: list
l3: list
l4:

a: int
b: str
c:
l1: list
l2: list

s1: str
s2:
w: int
x: int
y: int
z: int

a: int
b: int
c: str

x: int
y: str
z:

l1=[4,5,6]
l2=[“s1″,”s2″,”s3″]
l3=l1+l2
l4=l1*l2
k1=”input”
k2=”output”
k3=k1*k2
k4=k1+k2