How do I map from each letter a-z to the number of times the letter appears in the string?

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I need to return a dictionary which maps from each letter a-z (the keys), ignoring case, to the number of times this letter appears in the string (the values), if the letter appears in the string (all counts should be ≥1). Can somebody please explain to me why my code doesn't work?

Output I'm testing on:

assert(frequency_analysis("Hello world!") == {'h': 1, 'e': 1, 'l': 3, 'o': 2, 'w': 1, 'r': 1, 'd': 1})

What I have tried:

def frequency_analysis(string):
    freq = {}
    for character in string: 
        freq[character] = freq.get(character, 0) + 1
    return freq

Posted 18-Sep-20 6:08am

Sure shot

Updated 18-Sep-20 6:49am

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Richard MacCutchan · Answer 1 · 2020-09-18T06:18:00

Solution 1

Firstly you need to convert uppercase characters to lowercase, before adding them. Secondly you need to ignore special characters: space, !, ", £, etc.

Posted 18-Sep-20 6:18am

Richard MacCutchan

Updated 18-Sep-20 6:41am

v2

Patrice T · Answer 2 · 2020-09-18T06:49:00

Quote:
somebody please explain to me why my code doesn't work?

You forgot to tell us how the result is wrong.

Your code do not behave the way you expect, or you don't understand why !

There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

27.3. pdb — The Python Debugger — Python 3.6.1 documentation[^]
Debugging in Python | Python Conquers The Universe[^]
pdb – Interactive Debugger - Python Module of the Week[^]

The debugger is here to only show you what your code is doing and your task is to compare with what it should do.