Sometimes, while working with Python we can have a problem in which we have a list of records in form of tuples in stringified form and we desire to convert them to a list of tuples. This kind of problem can have its occurrence in the data science domain. Let’s discuss certain ways in which this task can be performed.
Method 1 (Using eval() + list comprehension): This problem can be easily performed as a one-liner using the inbuilt function of eval(), which performs this task of string to tuple conversion and list comprehension.
Python3
# Python3 code to demonstrate working of# Converting string tuples to list tuples# using list comprehension + eval()# Initializing listtest_list = ["('gfg', 1)", "('is', 2)", "('best', 3)"]# printing original listprint("The original list is : " + str(test_list))# Converting string tuples to list tuples# using list comprehension + eval()res = [eval(ele) for ele in test_list]# printing resultprint("The list tuple after conversion : " + str(res)) |
The original list is : ["('gfg', 1)", "('is', 2)", "('best', 3)"]
The list tuple after conversion : [('gfg', 1), ('is', 2), ('best', 3)]
Time complexity: O(n), where n is the length of the input list.
Auxiliary space: O(n), as we are creating a new list with the same length as the input list.
Method 2 (Using eval() + map()): This task can also be performed using a combination of the above functions. The task performed by list comprehension above can be performed using a map() in this method.
Python3
# Python3 code to demonstrate working of# Converting string tuples to list tuples# using map() + eval()# Initializing listtest_list = ["('gfg', 1)", "('is', 2)", "('best', 3)"]# printing original listprint("The original list is : " + str(test_list))# Converting string tuples to list tuples# using map() + eval()res = list(map(eval, test_list))# printing resultprint("The list tuple after conversion : " + str(res)) |
The original list is : ["('gfg', 1)", "('is', 2)", "('best', 3)"]
The list tuple after conversion : [('gfg', 1), ('is', 2), ('best', 3)]
Time Complexity: O(n), where n is the number of elements in the input list.
Auxiliary Space: O(n), where n is the number of elements in the input list, for the output list.
Method 3: Using the enumerate function
Python3
s=["('gfg', 1)", "('is', 2)", "('best', 3)"]x= [eval(i) for a,i in enumerate(s)]print(x) |
[('gfg', 1), ('is', 2), ('best', 3)]
Time complexity: O(n), where n is the length of the list ‘s’.
Auxiliary space: O(n), where n is the length of the list ‘s’.
Method 4: Using map()+eval()
Python3
s=["('gfg', 1)", "('is', 2)", "('best', 3)"]x=list(map(eval,s))print(x) |
[('gfg', 1), ('is', 2), ('best', 3)]
The time complexity of the program is O(n), where n is the length of the list “s”.
The auxiliary space complexity of the program is also O(n), as the list “x” has to store n elements, where n is the length of the input list “s”.
Method#5: Using Regex method.
Python3
# Python3 code to demonstrate working of# Converting string tuples to list tuples# Using regeximport re# Initializing listtest_list = ["('gfg', 1)", "('is', 2)", "('best', 3)"]# printing original listprint("The original list is : " + str(test_list))# Converting string tuples to list tuples# using regexres = [tuple(map(int, re.findall(r'\d+', i))) if j.isdigit() else (j.strip("(')"), int(k)) for i in test_list for j, k in re.findall(r"\('(.*?)', (.*?)\)", i)]# printing resultprint("The list tuple after conversion : " + str(res))#this code contributed by tvsk |
The original list is : ["('gfg', 1)", "('is', 2)", "('best', 3)"]
The list tuple after conversion : [('gfg', 1), ('is', 2), ('best', 3)]
Time Complexity: O(n)
Auxiliary Space: O(n)
Method 6: (Using ast.literal_eval() instead of eval())
The ast module provides a safer way to evaluate string literals. The ast.literal_eval() function can evaluate a string containing a Python expression or a container object literal and return the corresponding object. It only evaluates literals, so it won’t execute arbitrary code like eval().
Python3
import ast# Initializing listtest_list = ["('gfg', 1)", "('is', 2)", "('best', 3)"]# printing original listprint("The original list is : " + str(test_list))# Converting string tuples to list tuples# using ast.literal_eval() instead of eval()# ast.literal_eval() is a safer way to evaluate string literals# it only evaluates literals, so it won't execute arbitrary code like eval()res = [ast.literal_eval(ele) for ele in test_list]# printing resultprint("The list tuple after conversion : " + str(res)) |
The original list is : ["('gfg', 1)", "('is', 2)", "('best', 3)"]
The list tuple after conversion : [('gfg', 1), ('is', 2), ('best', 3)]
Time Complexity: O(n)
Auxiliary Space: O(n)
