Simple Python nested strings and slicing assignment. At least it should be but,

Question

 Simple Python nested strings and slicing assignment. At least it should be but, I'm having issues and looking to compare coding to figure out where I'm going wrong. Thank you in advance! :)  

 def process_matrix(matrix):     """     process a 2-D list:     Finish this function which accepts a 2-D(nested) list and calculate the sum of all the item in this 2-D matrix.     For example, a 2-D matrix may look like [[1,3],[2,4]]. The first list [1, 3] is the first line and [2, 4] is the 2nd line:     [ [1, 3],       [2, 4] ]     You can assume that there are multiple lines of this matrix and each line has multiple values     The return value should be the sum.     """ 

 # test my_2d_list = [[88,1], [5,67], [52,60,7]] print(process_matrix(my_2d_list))  # should b 280 print("--"*10) 

 def largest_diagonal_value(matrix):     """     process a 2-D list with if-else statements:     Finish this function which finds the largest diagonal value in a matrix.     A diagonal value of a matrix is a value which has the same row index and column index.     For the matrix below:     [ [1, 3],       [2, 4] ]     1 and 4 are the diagonal values.     You can assume that the parameter, matrix, is a non-empty n-by-n matrix.     The return value should be the largest diagonal value.     Hint: you can handle this question with one loop.     """  

 #test my_4_by_4 = [     [1,2,3,4],     [11,22,33,44],     [61,-62,63,64],     [49,64,81,100] ] print(largest_diagonal_value(my_4_by_4))   # 100 print("--"*10) 

 def has_negative_value_in_matrix(matrix):     """     process a 2-D list with nested loops and if-else:     Finish this function which checks whether the parameter, matrix, has any negative value.     This function should always return a boolean.     """ 

 #test print(has_negative_value_in_matrix(my_4_by_4))   #True print(has_negative_value_in_matrix(my_2d_list))   #False print("--"*10) 

Explanation / Answer

def process_matrix(matrix):
"""
process a 2-D list:
Finish this function which accepts a 2-D(nested) list and calculate the sum of all the item in this 2-D matrix.
For example, a 2-D matrix may look like [[1,3],[2,4]]. The first list [1, 3] is the first line and [2, 4] is the 2nd line:
[ [1, 3],
[2, 4] ]
You can assume that there are multiple lines of this matrix and each line has multiple values
The return value should be the sum.
"""
sum2D = 0
for row in matrix:
for cell in row:
sum2D += cell
return sum2D
# test
my_2d_list = [[88,1], [5,67], [52,60,7]]
print(process_matrix(my_2d_list)) # should b 280
print("--"*10)

def largest_diagonal_value(matrix):
"""
process a 2-D list with if-else statements:
Finish this function which finds the largest diagonal value in a matrix.
A diagonal value of a matrix is a value which has the same row index and column index.
For the matrix below:
[ [1, 3],
[2, 4] ]
1 and 4 are the diagonal values.
You can assume that the parameter, matrix, is a non-empty n-by-n matrix.
The return value should be the largest diagonal value.
Hint: you can handle this question with one loop.
"""
maxDiagonal = matrix[0][0]
for i in range(len(matrix)):
if maxDiagonal < matrix[i][i]:
maxDiagonal = matrix[i][i]
return maxDiagonal
#test
my_4_by_4 = [
[1,2,3,4],
[11,22,33,44],
[61,-62,63,64],
[49,64,81,100]
]
print(largest_diagonal_value(my_4_by_4)) # 100
print("--"*10)

def has_negative_value_in_matrix(matrix):
"""
process a 2-D list with nested loops and if-else:
Finish this function which checks whether the parameter, matrix, has any negative value.
This function should always return a boolean.
"""
for row in matrix:
for cell in row:
if cell < 0:
return True
return False
#test
print(has_negative_value_in_matrix(my_4_by_4)) #True
print(has_negative_value_in_matrix(my_2d_list)) #False
print("--"*10)

# copy pastable code link: https://paste.ee/p/R8bvr

Sample output

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