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Python program to convert camel case string to snake case

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Examples :

  Input:  GeeksForGeeks  Output:  geeks_for_geeks  Input:  ThisIsInCamelCase  Output:  this_is_in_camel_case 

Let’s see how we can accomplish this task.

Method # 1: Naive approach

This is a naive implementation for converting camel craft into snake craft. First, we initialize the res variable with an empty list and add the first (lowercase) character to it. Now, every time we come across an uppercase alphabet, we add & # 39; _ & # 39; and the alphabet (lowercase) to & # 39; res & # 39;, otherwise just add the alphabet only.

# Python3 string conversion program
# from camel to snake

 

def change_case ( str ):

res = [ str [ 0 ]. Lower ()]

for c in str [ 1 :]:

  if c in ( ’ ABCDEFGHIJKLMNOPQRSTUVWXYZ’ ):

res.append ( ’ _’ )

res.append (c.lower ())

else :

  res.append (c)

  

return ’’ .join (res)

 
# Driver code

str = "GeeksForGeeks"

print (change_case ( str ))

Exit :

 geeks_for_geeks 

Method # 2: Understanding the List

# Python3 string conversion program
# camel to snake

 

def change_case ( str ):

 

  return ’ .join ([’ _’ + i.lower () if i.isupper () 

else i for i in str ]). lstrip ( ’_’ )

 
# Driver code

str = "GeeksForGeeks"

print (change_case ( str ))

Exit:

 geeks_for_geek s 

Method # 3: Python Reduce ()

The Python Reduce () method applies function to all string alphabets, wherever it finds capital letters, it adds "_" in front of it and replaces capital letters with lowercase ones.

# Python3 conversion program lines
# from camel to snake

from functools import reduce

 

def change_case ( str ):

 

  return reduce ( lambda x, y: x + ( ’_’ if y.isupper () else ’’) + y, str ). lower ()

 
# Driver code

str = "GeeksForGeeks"

print (change_case ( str ))

Exit:

 geeks_for_geeks 

Method # 4: Python Regex

# Python3 string conversion program
# from camel to snake

import re

  

def change_case ( str ):

  s1 = re.sub ( ’(.) ([AZ] [az] +)’ , r ’1_2 ’ , str )

return re.sub ( ’([a-z0-9]) ([AZ])’ , r ’ 1_2’ , s1) .lower ()

 
# Driver code

str = "GeeksForGeeks"

print (change_case ( str ))

Exit:

 geeks_for_geeks 

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