w3resource

Python: Check the priority of the four operators

Python Basic - 1: Exercise-15 with Solution

Write a Python program to check the priority of the four operators (+, -, *, /).

Sample Solution:

Python Code:

from collections import deque
import re

__operators__ = "+-/*"
__parenthesis__ = "()"
__priority__ = {
    '+': 0,
    '-': 0,
    '*': 1,
    '/': 1,
}

def test_higher_priority(operator1, operator2):
    return __priority__[operator1] >= __priority__[operator2]

print(test_higher_priority('*','-'))
print(test_higher_priority('+','-'))
print(test_higher_priority('+','*'))
print(test_higher_priority('+','/'))
print(test_higher_priority('*','/'))

Sample Output:

True
True
False
False
True

Flowchart:

Flowchart: Python - Check the priority of the four operators

Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:

Python Code Editor :

 

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Write a Python program to add two positive integers without using the '+' operator.
Next: Write a Python program to get the third side of right angled triangle from two given sides.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Python: Tips of the Day

How to make a flat list out of list of lists?

Given a list of lists l

flat_list = [item for sublist in l for item in sublist]

which means:

flat_list = []
for sublist in l:
    for item in sublist:
        flat_list.append(item)

is faster than the shortcuts posted so far. (l is the list to flatten.) Here is the corresponding function:

flatten = lambda l: [item for sublist in l for item in sublist]

As evidence, you can use the timeit module in the standard library:

$ python -mtimeit -s'l=[[1,2,3],[4,5,6], [7], [8,9]]*99' '[item for sublist in l for item in sublist]'
10000 loops, best of 3: 143 usec per loop
$ python -mtimeit -s'l=[[1,2,3],[4,5,6], [7], [8,9]]*99' 'sum(l, [])'
1000 loops, best of 3: 969 usec per loop
$ python -mtimeit -s'l=[[1,2,3],[4,5,6], [7], [8,9]]*99' 'reduce(lambda x,y: x+y,l)'
1000 loops, best of 3: 1.1 msec per loop

Explanation: the shortcuts based on + (including the implied use in sum) are, of necessity, O(L**2) when there are L sublists -- as the intermediate result list keeps getting longer, at each step a new intermediate result list object gets allocated, and all the items in the previous intermediate result must be copied over (as well as a few new ones added at the end). So, for simplicity and without actual loss of generality, say you have L sublists of I items each: the first I items are copied back and forth L-1 times, the second I items L-2 times, and so on; total number of copies is I times the sum of x for x from 1 to L excluded, i.e., I * (L**2)/2.

The list comprehension just generates one list, once, and copies each item over (from its original place of residence to the result list) also exactly once.

Ref: https://bit.ly/3dKsNTR