﻿ Python Math: Parse math formulas and put parentheses around multiplication and division - w3resource # Python Math: Parse math formulas and put parentheses around multiplication and division

## Python Math: Exercise-60 with Solution

Write a Python program to parse math formulas and put parentheses around multiplication and division.

Sample Solution:-

Python Code:

``````#https://gist.github.com/ohaz/ed0b14a487b0569aad2d
import ast

def recurse(node):
if isinstance(node, ast.BinOp):
if isinstance(node.op, ast.Mult) or isinstance(node.op, ast.Div):
print('(', end='')
recurse(node.left)
recurse(node.op)
recurse(node.right)
if isinstance(node.op, ast.Mult) or isinstance(node.op, ast.Div):
print(')', end='')
print('+', end='')
elif isinstance(node, ast.Sub):
print('-', end='')
elif isinstance(node, ast.Mult):
print('*', end='')
elif isinstance(node, ast.Div):
print('/', end='')
elif isinstance(node, ast.Num):
print(node.n, end='')
else:
for child in ast.iter_child_nodes(node):
recurse(child)

def search_expr(node):
returns = []
for child in ast.iter_child_nodes(node):
if isinstance(child, ast.Expr):
return child
returns.append(search_expr(child))
for ret in returns:
if isinstance(ret, ast.Expr):
return ret
return None

formula = '4+5*7/2'

a = ast.parse(formula)

expr = search_expr(a)
if expr is not None:
recurse(expr)
print()
```
```

Sample Output:

```4+((5*7)/2)
```

Flowchart: Python Code Editor:

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## Python: Tips of the Day

Python: Get the Key Whose Value Is Maximal in a Dictionary

```>>> model_scores = {'model_a': 100, 'model_z': 198, 'model_t': 150}
>>> # workaround
>>> keys, values = list(model_scores.keys()), list(model_scores.values())
>>> keys[values.index(max(values))]
'model_z'
>>> # one-line
>>> max(model_scores, key=model_scores.get)
'model_z'
```