I am a beginner at Python, and to those who holds negative thoughts against my post, please leave. I am simply seeking help here and trying to learn. I'm trying to check within a simple data set the 0s and 1s. This will be used towards defining voids and solids on floor plans to define zones in buildings... eventually 0s and 1s will be swapped out with coordinates.
I am getting this error: ValueError: [0, 3] is not in list
I am simply checking if one list is contained in the other.
currentPosition's value is [0, 3]
subset, [[0, 3], [0, 4], [0, 5], [1, 3], [1, 4], [1, 5], [2, 1], [3, 1], [3, 4], [3, 5], [3, 6], [3, 7]]
Here's the code snippet:
def addRelationship(locale, subset):
subset = []; subSetCount = 0
for rowCount in range(0, len(locale)):
for columnCount in range (0, int(len(locale[rowCount])-1)):
height = len(locale)
width = int(len(locale[rowCount]))
currentPosition = [rowCount, columnCount]
currentVal = locale[rowCount][columnCount]
print "Current position is:" , currentPosition, "=", currentVal
if (currentVal==0 and subset.index(currentPosition)):
subset.append([rowCount,columnCount])
posToCheck = [rowCount, columnCount]
print "*********************************************Val 0 detected, sending coordinate to check : ", posToCheck
newPosForward = checkForward(posToCheck)
newPosBackward = checkBackward(posToCheck)
newPosUp = checkUpRow(posToCheck)
newPosDown = checkDwnRow(posToCheck)
I am using subset.index(currentPosition) to check and see if [0,3] is in subset but getting the [0,3] is not in list. How come?
index() method raises a 'ValueError' if specified item is not found in the list.
The method index() returns the lowest index in the list where the element searched for appears. If any element which is not present is searched, it returns a ValueError.
The Python IndexError: list index out of range can be fixed by making sure any elements accessed in a list are within the index range of the list. This can be done by using the range() function along with the len() function.
To fix this, you can modify the parameter in the range() function. A better solution is to use the length of the list as the range() function's parameter. The code above runs without any error because the len() function returns 3. Using that with range(3) returns 0, 1, 2 which matches the number of items in a list.
Let's show some equivalent code that throws the same error.
a = [[1,2],[3,4]]
b = [[2,3],[4,5]]
# Works correctly, returns 0
a.index([1,2])
# Throws error because list does not contain it
b.index([1,2])
If all you need to know is whether something is contained in a list, use the keyword in
like this.
if [1,2] in a:
pass
Alternatively, if you need the exact position but don't know if the list contains it, you can catch the error so your program does not crash.
index = None
try:
index = b.index([0,3])
except ValueError:
print("List does not contain value")
subset.index(currentPosition)
evaluates False
when currentPosition
is at index 0 of subset
, so your if
condition fails in that case. What you want is probably:
...
if currentVal == 0 and currentPosition in subset:
...
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