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Python – Itertools.dropwhile()

  • Last Updated : 19 Feb, 2020

Itertools is a Python module that provide various functions that work on iterators to produce complex iterators. It makes the code faster, memory efficient and thus we see a better performance. This module is either used by themselves or in combination to form iterator algebra.

Note: For more information, refer to Python Itertools

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Dropwhile()

The dropwhile() function of Python returns an iterator only after the func. in argument returns false for the first time.



Syntax:

dropwhile(func, seq):

Example 1:




# Python code to demonstrate the working of   
# dropwhile() 
  
  
# Function to be passed
# as an argument
def is_positive(n):
    return n > 0 
  
value_list =[5, 6, -8, -4, 2]
result = list(itertools.dropwhile(is_positive, value_list)) 
   
print(result) 

Output:

[-8, -4, 2]

Example 2:




# Python code to demonstrate the working of   
# dropwhile() 
    
    
import itertools 
    
    
# initializing list   
li = [2, 4, 5, 7, 8]  
      
# using dropwhile() to start displaying after condition is false  
print ("The values after condition returns false : ", end ="")  
print (list(itertools.dropwhile(lambda x : x % 2 == 0, li))) 

Output:

The values after condition returns false : [5, 7, 8]



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