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Python – Test if all digits starts from % K digit
  • Last Updated : 27 Feb, 2020

Sometimes we may face a problem in which we need to find for a list if it contains numbers which are % K. This particular utility has an application in day-day programming. Let’s discuss certain ways in which this task can be achieved.

Method #1 : Using list comprehension + map()
We can approach this problem by converting the elements to the strings and then testing the starting element of string and if they are % K we can return true and then convert to set and test for size of result to be one. The conversion is done by map, set function converts to set and list comprehension checks for first element of string.

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# Python3 code to demonstrate 
# Test if all digits starts from % K digit
# using list comprehension + map() 
  
# initializing list 
test_list = [65, 3, 92, 332
  
# printing original list 
print("The original list : " + str(test_list)) 
  
# initializing K 
K = 3
  
# using list comprehension + map() 
# Test if all digits starts from % K digit
res = len(set( not(int(sub[0]) % K) for sub in map(str, test_list))) == 1
  
# print result 
print("Does each element start with % K digit ? " + str(res)) 

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Output :

The original list : [65, 3, 92, 332]
Does each element start with % K digit ? True

 

Method #2 : Using all() + list comprehension
This is yet another approach in which this problem can be solved. In this we use all function to check for all elements and return a Boolean result and list comprehension does the part of conversion of string by str function and checking for all elements with the first digit of first element to be % K.



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brightness_4
code

# Python3 code to demonstrate 
# Test if all digits starts from % K digit
# using all() + list comprehension 
  
# initializing list 
test_list = [65, 3, 92, 332
  
# printing original list 
print("The original list : " + str(test_list)) 
  
# initializing K
K = 3
  
# using all() + list comprehension 
# Check if front digit is Odd in list 
res = not all(int(str(i)[0]) % K for i in test_list) 
  
# print result 
print("Does each element start with % K digit ? " + str(res)) 

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Output :

The original list : [65, 3, 92, 332]
Does each element start with % K digit ? True

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