How to convert a list of strings to ints in Python? You can use list comprehension or the map() function to convert a list of strings to ints in one line very efficiently. You can use other ways of Python to convert a list of strings to integers like for loop, eval(), ast.literal_eval(), and numpy.array() functions. In this article, I will explain how to convert a list of strings to ints by using all these functions with examples.
Related: You can also convert a list of integers to a string in Python.
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1. Quick Examples of Converting List of Strings to Ints
If you are in a hurry, below are some quick examples of converting a list of strings to ints.
# Quick examples of convert list of strings to ints
import ast
import numpy as np
# Initialize the list of strings
string_list = ["3", "6", "12", "9", "18"]
# Example 1: Using for loop
# Convert list of strings to integers
for i in range(0, len(string_list)):
string_list[i] = int(string_list[i])
# Example 2: Using list comprehension
# Convert list of strings to integers
int_list = [int(x) for x in string_list]
# Example 3: Using map() function
# Convert list of strings to integers
int_list = list(map(int, string_list))
# Example 4: Using eval() function
# Convert list of strings to integers
int_list = [eval(i) for i in string_list]
# Example 5: Using ast.literal_eval() function
# Convert list of strings to integers
int_list = [ast.literal_eval(i) for i in string_list]
# Example 6: Using numpy.array() function
my_array = np.array(string_list, dtype=int)
int_list = list(my_array)
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2. Convert List of Strings to Integers Using For Loop
To convert a list of strings to integers using a for loop in Python. For instance, you can initialize a list of strings string_list containing numerical values as strings. Then you can iterate through each element string_list using a for loop and convert each element from a string to an integerusing the int() function. The converted integers are stored back in the original list. After this loop, the string_list contains integers instead of strings.
# Initialize the list of strings
string_list = ["3", "6", "12", "9", "18"]
print("Original string:", string_list)
# Using for loop
# Convert list of strings to integers
for i in range(0, len(string_list)):
string_list[i] = int(string_list[i])
print("After converting a list of strings to integers:", string_list)
Yields below output.
This shows that the list of strings has been successfully converted to a list of integers.
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3. Convert List of Strings to Integers Using List Comprehension
You can also convert a list of strings to integers using list comprehension. In this code, the list comprehension [int(x) for x in string_list] iterates through each element x in string_list and converts it to an integer using the int() function. The resulting list of integers is stored in the variable int_list.
List comprehension provides a concise and readable way to convert a list of strings to a list of integers.
Related: You can convert a list to an integer in Python.
# Initialize the list of strings
string_list = ["3", "6", "12", "9", "18"]
print("Original string:",string_list)
# Using list comprehension
# Convert list of strings to integers
int_list = [int(x) for x in string_list]
print("After converting a list of strings to integers:", int_list)
Yields the same output as above.
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4. Convert List of Strings to Integers Using map() Function
Alternatively, you can use the map() function to convert a list of strings to integers and then convert the map object back to a list. For instance, the map(int, string_list) applies the int() function to each element string_list, converting them to integers. The map() function returns a map object, which is then converted back to a list using the list() function.
# Initialize the list of strings
string_list = ["3", "6", "12", "9", "18"]
print("Original string:",string_list)
# Using map() function
# Convert list of strings to integers
int_list = list(map(int, string_list))
print("After converting a list of strings to integers:", int_list)
Yields the same output as above.
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5. Convert List of Strings to Integers Using eval() Function
To convert a list of strings to integers using the eval() function in Python. For instance, you can initialize a list of strings containing numeric values, and then use the eval() function to convert these strings to integers.
In this code, the eval() function is used inside a list comprehension to evaluate each element string_list and convert it into an integer. The resulting int_list contains the converted integers.
# Initialize the list of strings
string_list = ["3", "6", "12", "9", "18"]
print("Original string:",string_list)
# Using eval() function
# Convert list of strings to integers
int_list = [eval(i) for i in string_list]
print("After converting a list of strings to integers:", int_list)
Yields the same output as above.
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6. Using the ast.literal_eval() function from the ast Module
To convert a list of strings representing integers into a list of actual integers using the ast.literal_eval() function. For instance, first, import the ast module, which provides a safe way to evaluate and parse expressions using the Python literal syntax. Then initializes a list of strings where each string represents a number.
Uses a list comprehension to iterate through each string string_list and apply ast.literal_eval() to convert the string to its corresponding integer representation. The resulting integers are stored in the int_list variable.
import ast
# Initialize the list of strings
string_list = ["3", "6", "12", "9", "18"]
print("Original string:",string_list)
# Using ast.literal_eval() function
# Convert list of strings to integers
int_list = [ast.literal_eval(i) for i in string_list]
print("After converting a list of strings to integers:", int_list)
Yields the same output as above.
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7. Using numpy.array() Function
Finally, you can use NumPy, a powerful library for numerical computing in Python, to convert a list of strings to integers. In this code, the np.array() function from NumPy is used to create a NumPy array of integers from the string_list. The dtype=int argument ensures that the elements are treated as integers. Then, the NumPy array is converted back to a Python list using the list() function, resulting in int_list containing integers.
import numpy as np
# Initialize the list of strings
string_list = ["3", "6", "12", "9", "18"]
print("Original string:",string_list)
# Using numpy.array() function
my_array = np.array(string_list, dtype=int)
int_list = list(my_array)
print("After converting a list of strings to integers:", int_list)
Yields the same output as above.
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Conclusion
In this article, I have explained how to convert a list of strings to ints in Python by using for loop, list comprehension, map(), eval(), ast.literal_eval(), and numpy.array() functions with examples.
Happy Learning !!
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