syntax error when instantiating object through eval()

Question

I'm writing as a final project for an independent study and I am currently working on some backbone code for it. I created a class called Chip and I am trying to automate instantiating objects as I have some 50 objects to instantiate. My code is as follows:

ChipLookup.py

class Chip:
    def __init__(self, name, function, type, datasheet, pinout):
        self.name = name.lstrip('x')
        self.function =  function.strip()
        self.type = type.strip()
        self.datasheet = datasheet.strip()
        self.pinout = pinout.strip()

#used to provide a string to eval later
def string_output(a, b, c):
        x = a[b][c]
        return x

def main():
    RawChipList = []

    for line in open('ChipDB.txt'):
        RawChipList.append(line)

    #parses the data from ChipDB.txt
    def data_split(a):
        N = []
        a = a.strip("\n")
        N = a.split(",")
        return N

    M = range(len(RawChipList))
    List = []
    Chips = []

    for i in  M:
        List.append(data_split(RawChipList[i]))
        eval('{0} = Chip(List[i][0], List[i][1], List[i][2], List[i][3], List[i][4])'.format(string_output(List, i, 0)))
        #error above, I am trying to create a Chip Object under the name List[i][0], so for example the first would be x74sn00
        Chips.append(generator(List, i, 0))

    return (M, Chips, List)

A few lines from ChipDB.txt. The last two fields on each line are going to be files, so they have not been filled yet. (note: There is a space after the last comma on each line)

ChipDB.txt

x74sn00, Quad 2 input NAND, NAND, , 
x74sn02, Quad 2-input NOR Gate, NOT, , 
x74sn04, Hex Inverter, Invert, , 
x74sn08, Quad 2-input AND Gate, AND, ,  
x74sn10, Triple 3-input NAND Gate, NAND, ,

The error I'm getting is: (note: this is when I import it interactively)

Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
  File "ChipLookup.py", line 31, in main
    eval('{0} = Chip(List[i][0], List[i][1], List[i][2], List[i][3], List[i][4])'.format(str(generator(List, i, 0))))
  File "<string>", line 1
    x74sn00 = Chip(List[i][0], List[i][1], List[i][2], List[i][3], List[i][4])
            ^
SyntaxError: invalid syntax

However, when I define Chip interactively and type the code

x74sn00 = Chip('x74sn00, 'quad 2 input NAND', 'NAND', ' ', ' ')

It works fine. What am I doing wrong here?

[what is the difference between eval/exec/compile](http://stackoverflow.com/questions/2220699/whats-the-difference-between-eval-exec-and-compile-in-python/2220790) — Antti Haapala -- Слава Україні, May 03 '15 at 04:47
also, you cannot use `exec` to introduce local variables in Python 3 anymore — Antti Haapala -- Слава Україні, May 03 '15 at 04:48
possible duplicate of [eval SyntaxError: invalid syntax in python](http://stackoverflow.com/questions/22558548/eval-syntaxerror-invalid-syntax-in-python) — abcd, May 03 '15 at 05:02
http://stackoverflow.com/help/how-to-ask http://stackoverflow.com/help/mcve — GreenAsJade, May 03 '15 at 05:09
Can anybody recommend how I could go about automating instantiating chip objects then? — MicArn, May 03 '15 at 14:27

score 0 · Answer 1 · answered May 03 '15 at 04:59

You can't make assignments using eval.

In [18]: eval('x = 1')
  File "<string>", line 1
    x = 1
      ^
SyntaxError: invalid syntax


In [19]: x = 1

In [20]: eval('x + 1')
Out[20]: 2

See the discussion at the link provided in the comments by @AnttiHaapala for information about other options.

syntax error when instantiating object through eval()

1 Answers1