TypeError: list indices must be integers or slices, not tuple while doing some calculation in a nested list

问题:

I am trying to do some calculation in nested lists

The example is [['Amy',2,3,4],['Jack',3,4,None]], and I want to see the output like: [[3.0,'Amy'],[3.5,'Jack']](3.0 is mean of 2,3,4 and 3.5 is mean of 3,4)

My code:

def compute_mean_pc():     students_pclist=[['Amy',2,3,4],['Jack',3,4,None]]     mean_pc=[[[countMean(students_pclist[element][1:])]for element in enumerate(students_pclist)]+[element[0]]for element in students_pclist]     print(mean_pc)   def countMean(array):     count=0     sumup=0     for i in range(len(array)):         if array[i]!=None:             count+=1             sumup+=array[i]     mean=sumup/count     return mean  compute_mean_pc() 

the second part, countMean(array) works well, but for the first part,in this line

mean_pc=[[[countMean(students_pclist[element][1:])]for element in enumerate(students_pclist)]+[element[0]]for element in students_pclist] 

Python returns a type error: list indices must be integers or slices, not tuple

What's wrong with my code?

回答1:

The wrong part in your code is for element in enumerate(students_pclist) inside your list comprehension: enumerate() returns a tuple on each iteration loop. So you should have written something like for element,i in enumerate(students_pclist). It fixes your error, but it does not give you the expected answer.

Here is a suggestion of complete fix, based on your code:

myListOfLists = [['Amy',2,3,4], ['Jack',3,4,None]]  def compute_mean_pc():     students_pclist=[['Amy',2,3,4],['Jack',3,4,None]]     mean_pc=[ [countMean(student[1:])] +[student[0]] for student in students_pclist]     print(mean_pc)   def countMean(array):     count=0     sumup=0     for i in range(len(array)):         if array[i]!=None:             count+=1             sumup+=array[i]     mean=sumup/count     return mean  compute_mean_pc() #  [[3.0, 'Amy'], [3.5, 'Jack']] 

And finally I suggest you a code which is more efficient and still readable, using a good old-fashioned for loop:

myList = [['Amy',2,3,4], ['Jack',3,4,None]]  def compute_mean_pc(myList):     result = []     for name, *values in myList:            # iterate over each sub-list getting name and next values         values = list(filter(None,values))             # Remove any 'None' from the values          result.append([name, sum(values)/len(values)]) # Append a list [name,mean(values)] to the result list     return result  result = compute_mean_pc(myList)  print(result) # [['Amy', 3.0], ['Jack', 3.5]] 

回答2:

for element in enumerate(students_pclist) will assign a tuple (index, element_of_students_pclist) to element.

What you want is:

[[countMean(element[1:]), element[0]] for element in students_pclist] 

回答3:

You had problems with correctly using index returned by the enumerate. I just slightly modified your code with the correct way of using enumerate

def compute_mean_pc():     students_pclist=[['Amy',2,3,4],['Jack',3,4,None]]     mean_pc=[[ countMean(students_pclist[i][1:]) ] + [element[0]] for i, element in enumerate(students_pclist)]     print(mean_pc) 

Output

[[3.0, 'Amy'], [3.5, 'Jack']] 

回答4:

This one should do what you need:

a = [['Amy',2,3,4],['Jack',3,4,None]]  def computeMean(array):     valid = [i for i in array[1:] if i]     return [sum(valid)/len(valid)]  result = [computeMean(sub) + sub[:1] for sub in a] result #[[3.0, 'Amy'], [3.5, 'Jack']] 

回答5:

You can use below function to count mean:

def compute_mean_pc():     students_pclist=[['Amy',2,3,4],['Jack',3,4,None]]     mean_pc=[ [student[0], count_mean(student)]  for student in students_pclist]     print(mean_pc)   def count_mean(array):     grades = [el for el in array if isinstance(el, int)]     return sum(grades) / len(grades)  compute_mean_pc() 

文章来源: TypeError: list indices must be integers or slices, not tuple while doing some calculation in a nested list