I am trying to split an arithmetic equation into a list of terms and operators

Question

An examples of what im trying to do:

split('2.1     * -5    + 3    ^ 2 +     1 +    -4.45')

should output

[2.1,'*',-5.0,'+',3.0,'^',2.0,'+',1.0,'+',-4.45]

my current code:

ops = ('+','-','*','/','^','(')

def split(txt):
    final = []
    temp = []
    inp = "".join(txt.split())
    for x in inp:
        if x.isdigit():
            temp.append(int(x))
        elif x == '.':
            temp.append(x)
        elif x in ops:
            if x == '-':
                if len(temp) == 0:
                    if isinstance(final[-1],float):
                        final.append(float("".join(temp)))
                        final.append(x)
                        temp = []
                    else:
                        temp.append(x)
                else:
                    final.append(float("".join(temp)))
                    final.append(x)
                    temp = []
            else:
                final.append("".join(temp))
                final.append(x)
                temp = []
    final.append(float("".join(temp)))
    print(final)

error, im not sure what im doing wrong here, and im not even sure if the code ive written is able to do what i want

Traceback (most recent call last):
  File "C:UsersSahil PrustiDesktopcmpsc132HW 3hwtest.py", line 32, in <module>
    print(split('2* (       -5.2 + 3 ) ^2+ ( 1 +4 )'))
  File "C:UsersSahil PrustiDesktopcmpsc132HW 3hwtest.py", line 26, in split
    final.append("".join(temp))
TypeError: sequence item 0: expected str instance, int found

Asked By: Sahil gaming

||

Source

Answer 1

In line 32, you split the string.

print(split('2* (       -5.2 + 3 ) ^2+ ( 1 +4 )'))

But what you are appending in line 26 is int, not string therefore, you have an error.

final.append("".join(temp))

try

final.append("".join(str(temp)))

Answered By: Konrad Niedźwiedzki

Answer 2

Don’t know exactly what is wrong with your program but you could reduce its complexity:

expr = '2.1     * -5    + 3    ^ 2 +     1 +    -4.45'

ops = ('+','-','*','/','^','(')

terms = expr.split()
print([float(t) if t not in ops else t for t in terms])
#[2.1, '*', -5.0, '+', 3.0, '^', 2.0, '+', 1.0, '+', -4.45]

For more sophisticated expressions a regular expression approach could be helpful.

Answered By: cards

Answer 3

How about:

s= '2.1     * -5    + 3    ^ 2 +     1 +    -4.45'

splitted = [x for x in s.split(' ') if x !=""]

result = []

for x in splitted:
    try:
         result.append(float(x))
    except ValueError:
        result.append(x)
      
print(result)

Answered By: user19077881

I am trying to split an arithmetic equation into a list of terms and operators

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