CODEWITHSUNDEEP
pythonpython-3.x
smallvt
smallvt

Reputation: 63

For loops with tuples

I am trying to figure out how to use a for loop to identify a quadrant that a point (defined by a tuple) is in.

The program prompts until a non-numerical answer is given. Then, using the points input by the user, I need to identify which quadrant each point would be in.

For example: points (0, 1),(1,2),(2,3), and (3,4) are stored in a list and need their quadrants identified by a for loop.

I am unsure where to start with this. My input code is as follows:

locationlist = []
count = 0

while True :
    try : 
        tup = input("Enter X and Y separated by a space, or enter a non-number to stop: ")
        x, y = tup.split()
        x = float(x)
        y = float(y)
        count = count + 1
        locationlist.append(tup)
    except ValueError:
        break
print("Points: ",locationlist)

Upvotes: 0

Views: 114

Answers (3)

Doyousketch2
Doyousketch2

Reputation: 2147

You don't need to create extra variables for that, just nest your test.

for x, y in locationList:
    if y >= 0:
        if x >= 0:  print( x, y, 'Quadrant 1' )
        else:     print( x, y, 'Quadrant 2' )
    else:  ##  y < 0
        if x < 0:  print( x, y, 'Quadrant 3' )
        else:     print( x, y, 'Quadrant 4' )

Edit: If axis is required:

for x, y in locationList:
    if y > 0:
        if x > 0:  print( x, y, 'Quadrant 1' )
        elif x < 0: print( x, y, 'Quadrant 2' )
        else:      print( x, y, 'pos Y-axis' )

    elif y < 0
        if x < 0:  print( x, y, 'Quadrant 3' )
        elif x > 0: print( x, y, 'Quadrant 4' )
        else:      print( x, y, 'neg Y-axis' )

    else:
        if x > 0:  print( x, y, 'pos X-axis' )
        elif x < 0: print( x, y, 'neg X-axis' )
        else:  print( x, y, 'Origin' )

Upvotes: 1

Adrian Keister
Adrian Keister

Reputation: 1025

I think I would use a divide-and-conquer strategy to reduce the number of comparisons. Perhaps something like this:

for x, y in locationList:

    # 2nd or 4th
    if x * y < 0:
        if x < 0:
            # Second quadrant.
        else:
            # Fourth quadrant.

    # 1st or 3rd
    elif x * y > 0:
        if x < 0:
            # Third quadrant.
        else:
            # First quadrant.

    # On an axis: quadrant not well-defined.
    else:
        # No quadrant.

Upvotes: 1

Adin Ackerman
Adin Ackerman

Reputation: 312

I believe this is what you are asking for:

for x, y in locationList:
    a = x > 0
    b = y > 0
    c = x == 0 or y == 0
    
    if not c:
        if a and b:
            # 1st quadrant
        elif a:
            # 4th quadrant
        elif b:
            # 2nd quadrant
        else:
            # 3rd quadrant
    else:
        # no quadrant

Basically what I'm doing is storing the conditions of whether x and y are positive or not, so that I can do logic on those without repeatedly calculating those conditions.

Upvotes: 2

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