Many times it is desirable to work with the strings that only contain alphabets and the other special characters are undesirable and sometimes this very task becomes the point to filter the strings and hence requires the way to check if a string is whole ASCII. Let’s discuss certain ways in which this task can be performed.
Method #1 : Using ord() + all() The combination of this method can be used to achieve the desirable task. In this method, we search for all the string and check for each character, a value in range of ASCII characters.
Python3
# Python3 code to demonstrate# Check for ASCII string# using all() + ord()# initializing string test_string = "G4G is best"# printing original string print("The original string : " + str(test_string))# using all() + ord()# Check for ASCII stringres = all(ord(c) < 128 for c in test_string)# print resultprint("Is the string full ASCII ? : " + str(res)) |
The original string : G4G is best Is the string full ASCII ? : True
Method #2 : Using lambda + encode() This task can also be achieved using the above functions. In this combination, lambda function is used to extend the size check logic to whole string and encode function checks if the size of original and encoded strings match.
Python3
# Python3 code to demonstrate# Check for ASCII string# using lambda + encode()# initializing string test_string = "G4G is best"# printing original string print("The original string : " + str(test_string))# using lambda + encode()# Check for ASCII stringres = lambda ele: len(ele) == len(ele.encode())# print resultprint("Is the string full ASCII ? : " + str(res(test_string))) |
The original string : G4G is best Is the string full ASCII ? : True
Method 3: Using re.search()
re.search() is a function from the Python re (regular expression) module. It searches for a pattern (in this case, a pattern that matches any ASCII character) within a string and returns a match object if found, or None if not found.
Python
import re # Import the re moduledef is_ascii(string): # Use re.search() to search for a pattern (in this case, a pattern that matches any ASCII character) # within the input string. The r prefix before the pattern string tells Python to treat the string as a raw string, # which is useful for patterns that contain backslashes. The ^ and $ symbols indicate that the pattern should # match the entire string (not just a substring). match = re.search(r'^[\x00-\x7F]+$', string) # Return a boolean value indicating whether a match was found (True if a match was found, False if not) return bool(match)# Test the functiontest_string = "G4G is best"print("The original string : " + str(test_string))print("Is the string full ASCII ? :", is_ascii(test_string))#This code is contributed by Edula Vinay Kumar Reddy |
The original string : G4G is best
('Is the string full ASCII ? :', True)
This function has a time complexity of O(n), where n is the length of the input string, since re.search() searches through the entire string. The auxiliary space is O(1), since the function only creates a single boolean variable to store the result.
Approach#4: Using string.printable()
The approach used here is to check whether each character in the string s is a printable ASCII character or not. We can use the string.printable constant to get all the printable ASCII characters, which includes digits, letters, punctuation, and whitespace. We can then iterate over the characters in the string s and check if each character is in string.printable using the in operator.
Algorithm
1. Define a function is_ascii that takes a string s as input.
2. Iterate over each character c in s.
3. Check if the character c is in string.printable using the in operator.
4. If any character c is not in string.printable, return False.
5. If all characters in s are in string.printable, return True
Python3
import stringdef is_ascii(s): """Return True if string s is ASCII, False otherwise.""" return all(c in string.printable for c in s)# Example usage:s = "G4G is best"print(is_ascii(s)) # Output: True |
True
Time Complexity: O(n), where n is the length of the input string s. This is because we need to iterate over each character in s once.
Space Complexity: O(1), which is constant. We are not using any additional data structures that depend on the input size. The string.printable constant is a fixed-length constant that does not depend on the length of the input string.
