Get the sum of numbers in a list of strings using Python

In Python, we can use various methods to sum numbers in a string list, such as using regular expressions, using isdigit() and list comprehensions, using splitting and concatenation, etc. When working with lists containing strings, you often encounter situations where you need to extract and sum numeric values ​​from these strings. This is especially useful when working with text files, log files, or web scraping, for example. In this article, we will use different examples and algorithms to understand these methods.

algorithm

The general algorithm for finding the sum of numbers in a list of strings using Python is as follows:

• Define a function that takes a list of strings as input.

• Concatenate all elements in the string list into a string.

• Apply a pattern or method to extract a numeric value from a string.

• Convert the extracted value to an integer.

• Sum a list of integers.

• Use the summation result as the return value.

Method 1: Use regular expressions

Regular expressions provide an efficient way to match patterns in strings. By defining a pattern and using the re.findall() function, we can extract all values ​​from a list of strings. These values ​​are then converted to integers and summed to get the final result.

grammar

numbers = [int(num) for num in re.findall(pattern, ''.join(string_list))]

Here, a list comprehension is used [int(num) for num in re.findall(pattern, ''.join(string_list))] Convert the matched string to an integer .

The Chinese translation of

Example

is:

Example

In the above example, we have a string_list containing three elements. Call the sum_numbers() function with string_list as argument. The regular expression pattern r"\d" matches one or more numbers in each element of the list. The matching numbers are extracted using list comprehensions and converted to integers. Finally, the sum() function calculates the sum of these numbers.

import re

def sum_numbers(string_list):
    pattern = r"\d+"
    numbers = [int(num) for num in re.findall(pattern, ''.join(string_list))]
    return sum(numbers)

string_list = ['abc123', 'def456', 'ghi789']
print(sum_numbers(string_list))

Output

1368

Method 2: Use isdigit() and list comprehension

This method uses the isdigit() method, which is used to check whether a character is a digit, combined with a list comprehension. By iterating through each character in the string list and filtering out non-numeric characters, we can convert the remaining numbers into integers. The resulting list is then summed to get the desired sum.

grammar

numbers = [int(char) for item in string_list for char in item if char.isdigit()]

Here, a list comprehension is used [int(char) for item in string_list for char in item if char.isdigit()] to iterate through each element in string_list character. isdigit() method is used to check whether a character is a digit.

The Chinese translation of

Example

is:

Example

In the example below, we have the same string_list as before. Call the sum_numbers() function with string_list as argument. The list comprehension iterates over each character in each element of string_list. The isdigit() method checks if a character is a digit and if so, converts it to an integer. Then use the sum() function to sum the resulting list of numbers.

def sum_numbers(string_list):
    numbers = [int(char) for item in string_list for char in item if char.isdigit()]
    return sum(numbers)

string_list = ['abc123', 'def456', 'ghi789']
print(sum_numbers(string_list))

Output

45

Method 3: Use Split and Join

In this method, the elements of the string list are concatenated into a single string using the join() method. The concatenated string is then split into a list of words. By iterating through each word and filtering out non-numeric words, we can convert the remaining words into integers. Finally, sum the resulting list of numbers to get the desired result.

grammar

numbers = ''.join(string_list).split()
 numbers = [int(num) for num in numbers if num.isdigit()]

Here, use the join() method to concatenate all elements of string_list into a string.

Then apply the split() method to the concatenated string to split it into a list of words. Use the list comprehension [int(num) for num in numbers if num.isdigit()] to iterate through each element in the numbers list and convert it to an integer if it contains only numbers.

The Chinese translation of

Example

is:

Example

In the following example, we use the filter() function and str.isdigit as filter conditions to extract only digits from each item of the string list. part. We then join the filtered numbers using ''.join() and convert the result to an integer using int().

def sum_numbers(string_list):
    numbers = [int(''.join(filter(str.isdigit, item))) for item in string_list]
    return sum(numbers)

string_list = ['abc123', 'def456', 'ghi789']
print(sum_numbers(string_list))

Output

1368

in conclusion

In this article, we discussed how to find the sum of numbers in a list of strings using different methods in Python. We discussed three methods: using regular expressions (re), leveraging the isdigit() method in list comprehensions, and using split and join operations. Each method has its own advantages and can be used depending on the specific requirements of the task.

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