Python - Remove strings with any non-required character

Python - Remove strings with any non-required character

Let's say you have a list of strings and you want to remove any string that contains a character which is not in a predefined set of allowed characters.

To achieve this, you can use a list comprehension and Python's built-in all() function.

Here's a step-by-step guide:

1. Sample Data:

Suppose you have the following list of strings:

strings = ["apple", "banana", "cherry!@", "date123", "egg!", "fish"]

Let's say you want to keep strings that only contain the characters a to z (i.e., lowercase alphabets).

2. Using List Comprehension:

Define the set of allowed characters:

allowed_chars = set("abcdefghijklmnopqrstuvwxyz")

Now, use a list comprehension to filter out the strings:

filtered_strings = [s for s in strings if all(char in allowed_chars for char in s)]

Print the filtered list:

print(filtered_strings) # Output: ['apple', 'banana', 'fish']

Explanation:

  • The inner comprehension char in allowed_chars for char in s checks each character in the string s to see if it's in the allowed set.
  • The all() function then ensures that every character in the string s is an allowed character.
  • If any character in s is not allowed, then all() will return False, and the string will not be included in the filtered_strings list.

Conclusion:

In this tutorial, we've demonstrated how to remove strings from a list in Python if they contain any non-required characters. By using list comprehensions combined with the all() function, we were able to efficiently filter the list based on a set of allowed characters.

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