A value in a list, python

Question

Every character in the English language has a percentage of occurrence, these are the percentages: ``` A B C D E F G H I .0817 .0149 .0278 .0425 .1270 .0223 .0202 .0609 .0697 J K L M N O P Q R .0015 .0077 .0402 .0241 .0675 .0751 .0193 .0009 .0599 S T U V W X Y Z .0633 .0906 .0276 .0098 .0236 .0015 .0197 .0007 ``` A list called `letterGoodness` is predefined as: ``` letterGoodness = [.0817,.0149,.0278,.0425,.1270,.0223,.0202,... ``` I need to find the "goodness" of a string. For example the goodness of 'I EAT' is: .0697 + .1270 + .0817 + .0906 =.369. This is part of a bigger problem, but I need to solve this to solve the big problem. I started like this: ``` def goodness(message): for i in L: for j in i: ``` So it will be enough to find out how to get the occurrence percentage of any character. Can you help me? The string contains only uppercase letters and spaces.

Accepted Answer

letterGoodness is better as a dictionary, then you can just do:

```
sum(letterGoodness.get(c,0) for c in yourstring.upper())
#                                             #^.upper for defensive programming
```

To convert `letterGoodness` from your list to a dictonary, you can do:

```
import string
letterGoodness = dict(zip(string.ascii_uppercase,letterGoodness))
```

If you're guaranteed to only have uppercase letters and spaces, you can do:

```
letterGoodness = dict(zip(string.ascii_uppercase,letterGoodness))
letterGoodness[' '] = 0
sum(letterGoodness[c] for c in yourstring)
```

but the performance gains here are probably pretty minimal so I would favor the more robust version above.

If you insist on keeping `letterGoodness` as a list (and I don't advise that), you can use the builtin `ord` to get the index (pointed out by cwallenpoole):

```
 ordA = ord('A')
 sum(letterGoodness[ord(c)-ordA] for c in yourstring if c in string.ascii_uppercase)
```

I'm too lazy to `timeit` right now, but you may want to also define a temporary set to hold `string.ascii_uppercase` -- It might make your function run a little faster (depending on how optimized `str.__contains__` is compared to `set.__contains__`):

```
 ordA = ord('A')
 big_letters = set(string.ascii_uppercase)
 sum(letterGoodness[ord(c)-ordA] for c in yourstring.upper() if c in big_letters)
```

A value in a list, python

Solution

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