Python - Check if frequencies of all characters of a string are different

In this article, we will see how to find the frequency of each character in a given string and check if all characters have different frequencies. We'll accomplish this in two steps: first calculating character frequencies, then checking if all frequencies are unique.

Finding Character Frequencies

We can count character frequencies using a dictionary. For each character in the string, we either increment its count or initialize it to 1 ?

Example

in_string = "She sells sea shells"
char_freq = {}

for char in in_string:
    if char in char_freq.keys():
        char_freq[char] += 1
    else:
        char_freq[char] = 1

print("Character frequencies:", char_freq)

for char in char_freq.keys():
    print(f"{char!r} repeats {char_freq[char]} time(s)")

Character frequencies: {'S': 1, 'h': 2, 'e': 4, ' ': 3, 's': 5, 'l': 4, 'a': 1}
'S' repeats 1 time(s)
'h' repeats 2 time(s)
'e' repeats 4 time(s)
' ' repeats 3 time(s)
's' repeats 5 time(s)
'l' repeats 4 time(s)
'a' repeats 1 time(s)

Checking if All Frequencies Are Different

To check if all characters have different frequencies, we extract all frequency values and convert them to a set. If the set length equals the dictionary length, all frequencies are unique ?

Example

in_string = "She sells sea shells"
char_freq = {}

for char in in_string:
    if char in char_freq.keys():
        char_freq[char] += 1
    else:
        char_freq[char] = 1

print("Character frequencies:", char_freq)

# Get unique frequency values
unique_frequencies = set(char_freq.values())
print("Unique frequencies:", unique_frequencies)
print("Number of unique frequencies:", len(unique_frequencies))

if len(unique_frequencies) == len(char_freq):
    print("All characters have different frequencies")
else:
    print("Some characters have the same frequency")

Character frequencies: {'S': 1, 'h': 2, 'e': 4, ' ': 3, 's': 5, 'l': 4, 'a': 1}
Unique frequencies: {1, 2, 3, 4, 5}
Number of unique frequencies: 5
Some characters have the same frequency

Using Collections.Counter Method

Python's collections.Counter provides a more elegant solution for counting character frequencies ?

from collections import Counter

def check_different_frequencies(string):
    # Count character frequencies
    char_freq = Counter(string)
    print("Character frequencies:", dict(char_freq))
    
    # Get unique frequency values
    frequencies = list(char_freq.values())
    unique_frequencies = set(frequencies)
    
    print("All frequencies:", frequencies)
    print("Unique frequencies:", unique_frequencies)
    
    # Check if all frequencies are different
    if len(unique_frequencies) == len(frequencies):
        return "All characters have different frequencies"
    else:
        return "Some characters have the same frequency"

# Test with different strings
test1 = "abc"
test2 = "She sells sea shells"

print("Testing:", test1)
print(check_different_frequencies(test1))
print("\nTesting:", test2)  
print(check_different_frequencies(test2))

Testing: abc
Character frequencies: {'a': 1, 'b': 1, 'c': 1}
All frequencies: [1, 1, 1]
Unique frequencies: {1}
Some characters have the same frequency

Testing: She sells sea shells
Character frequencies: {'S': 1, 'h': 2, 'e': 4, ' ': 3, 's': 5, 'l': 4, 'a': 1}
All frequencies: [1, 2, 4, 3, 5, 4, 1]
Unique frequencies: {1, 2, 3, 4, 5}
Some characters have the same frequency

Conclusion

To check if all characters have different frequencies, count character occurrences using a dictionary or Counter, then compare the number of unique frequencies with the total number of characters. Use set(frequencies) to find unique values efficiently.