Python | Convert string tuples to list tuples

Last Updated : 28 Feb, 2023

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 list
test_list = ["('gfg', 1)", "('is', 2)", "('best', 3)"]

# printing original list
print("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 result
print("The list tuple after conversion : " + str(res))

Output :

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 list
test_list = ["('gfg', 1)", "('is', 2)", "('best', 3)"]

# printing original list
print("The original list is : " + str(test_list))

# Converting string tuples to list tuples
# using map() + eval()
res = list(map(eval, test_list))

# printing result
print("The list tuple after conversion : " + str(res))

Output :

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)

Output

[('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)

Output

[('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 regex
import re
# Initializing list
test_list = ["('gfg', 1)", "('is', 2)", "('best', 3)"]

# printing original list
print("The original list is : " + str(test_list))

# Converting string tuples to list tuples
# using regex


res = [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 result
print("The list tuple after conversion : " + str(res))
#this code contributed by tvsk

Output

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 list
test_list = ["('gfg', 1)", "('is', 2)", "('best', 3)"]

# printing original list
print("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 result
print("The list tuple after conversion : " + str(res))

Output

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)

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