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Python | Find frequency of given character at every position in list of lists
  • Last Updated : 14 Nov, 2019

Given a list of lists, the task is to find the frequency of a character at every position of sub-list in list of lists.

Input : lst = [['X', 'Y', 'X'], ['Z', 'Y', 'X'],
               ['Y', 'Y', 'Y'], ['Z', 'Z', 'X'],
               ['Y', 'Z', 'X']], character = 'X'

Output: [0.2, 0.0, 0.8]

Explanation:
We have 3 elements in each sublist, we have to find position of ‘X’ at position 0, 1 and 2. For Position 0 in all sublist we have –
‘x’ in first sub list at zero position,
‘z’ in second sub list at zero position,
‘y’ in third sub list at zero position,
‘z’ in fourth sub list at zero position and
‘y’ in fifth sub list at zero position.

So, we have 1 occurrence of ‘x’ at position 1 in all sub list so, Occurrence = 1/5 = .2
For Position 1 we don’t have any occurrence of ‘x’ in sub list so, Occurrence = 0/5 = 0.
For Position 2 we have 4 occurrence of ‘x’ in sub list so, Occurrence = 4/5 = 0.8

 
Let’s discuss certain ways in which this can be performed.

Method #1 : Using Iteration






# Python code to find frequency of a character
# at every position of list in list of lists.
  
# Input list initialization
Input = [['X', 'Y', 'X'], ['Z', 'Y', 'X'],
         ['Y', 'Y', 'Y'], ['Z', 'Z', 'X'],
         ['Y', 'Z', 'X']]
Output = []
  
# Character Initialization
character = 'X'
  
# Output list initialization
for elem in range(len(Input[0])):
    Output.append(0)
  
# Using iteration
for elem in Input:
    for x, y in enumerate(elem):
        if y == character:
            Output[x]+= 1
for x, y in enumerate(Output):
    Output[x] = y / len(Input)
  
# Printing
print("Initial list of list is :", Input)
print("Occurrence of 'X' in list is", Output)
Output:

Initial list of list is : [[‘X’, ‘Y’, ‘X’], [‘Z’, ‘Y’, ‘X’], [‘Y’, ‘Y’, ‘Y’], [‘Z’, ‘Z’, ‘X’], [‘Y’, ‘Z’, ‘X’]]
Occurrence of ‘X’ in list is [0.2, 0.0, 0.8]

 
Method #2 : Using zip




# Python code to find frequency of a character
# at every position of list in list of lists.
  
# Input list initialization
Input = [['X', 'Y', 'X'], ['Z', 'Y', 'X'],
         ['Y', 'Y', 'Y'], ['Z', 'Z', 'X'],
         ['Y', 'Z', 'X']]
  
Output = []
  
# Character initialization
character = 'X'
  
# Using zip
Output = [elem.count(character)/len(elem)
                 for elem in zip(*Input)]
  
# Printing
print("Initial list of list is :", Input)
print("Occurrence of 'X' in list is", Output)
Output:

Initial list of list is : [[‘X’, ‘Y’, ‘X’], [‘Z’, ‘Y’, ‘X’], [‘Y’, ‘Y’, ‘Y’], [‘Z’, ‘Z’, ‘X’], [‘Y’, ‘Z’, ‘X’]]
Occurrence of ‘X’ in list is [0.2, 0.0, 0.8]

 
Method #3: Using Pandas




# Python code to find frequency of a character
# at every position of list in list of lists.
  
import pandas as pd
  
# Input list initialization
Input = [['X', 'Y', 'X'],
      ['Z', 'Y', 'X'],
      ['Y', 'Y', 'Y'],
      ['Z', 'Z', 'X'],
      ['Y', 'Z', 'X']]
  
# Defining character
character = 'X'
  
# using pandas
Output = pd.DataFrame(Input)
Output = Output.where(Output == character, 0).where(Output != character, 1)
  
# Printing
print("Initial list of list is :", Input)
print("Occurrence of 'X' in list is\n", Output.mean())
Output:

Initial list of list is : [[‘X’, ‘Y’, ‘X’], [‘Z’, ‘Y’, ‘X’], [‘Y’, ‘Y’, ‘Y’], [‘Z’, ‘Z’, ‘X’], [‘Y’, ‘Z’, ‘X’]]
Occurrence of ‘X’ in list is
0 0.2
1 0.0
2 0.8
dtype: float64

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