entityMap|blocks|key|97bii|text|这应该是可行的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4sfdp|>>>+from+collections+import+Counter
>>>+from+string+import+ascii_letters
>>>+def+count_letters(s)+:
...+++++filtered+=+[c+for+c+in+s.lower()+if+c+in+ascii_letters]
...+++++return+Counter(filtered)
...+
>>>+count_letters('Math+is+fun!+2%2B2=4')
Counter({'a':+1,+'f':+1,+'i':+1,+'h':+1,+'m':+1,+'n':+1,+'s':+1,+'u':+1,+'t':+1})
>>>+|code-block|syntax|javascript|5186v^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|J|9|@]|A|@]|B|$F|G]]|$2|H|4|-4|6|7|8|K|9|@]|A|@]|B|$]]]]

This should work:

<pre><code>&gt;&gt;&gt; from collections import Counter
&gt;&gt;&gt; from string import ascii_letters
&gt;&gt;&gt; def count_letters(s) :
... filtered = [c for c in s.lower() if c in ascii_letters]
... return Counter(filtered)
... 
&gt;&gt;&gt; count_letters('Math is fun! 2+2=4')
Counter({'a': 1, 'f': 1, 'i': 1, 'h': 1, 'm': 1, 'n': 1, 's': 1, 'u': 1, 't': 1})
&gt;&gt;&gt; 
</code></pre>

entityMap|blocks|key|ddruu|text|def+count_letters(text):
+r+=+{}
++#+Go+through+each+letter+in+the+text
+for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
+++++for+letter+in+text:
#+Check+if+the+letter+needs+to+be+counted+or+not
+for+alp+in+letter:
++#+To+check+the+letters+are+alphabets+or+not
++if+alp+in+ascii_letters:
+++#Converting+into+lowercase+as+python+is+case+sensitive
++++if+alp.lower()+in+r+and+alp!='+':
++++++r[alp.lower()]%2B=1
++++elif+alp.lower()+not+in+r+and+alp!='+':
++++++r[alp.lower()]=1
++#+Add+or+increment+the+value+in+the+dictionary
++return+r

print(count_letters("AaBbCc"))
print(count_letters("Math+is+fun!+2%2B2=4"))
print(count_letters("This+is+a+sentence."))|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2cmu3|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 r = {}
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 for letter in text:
# Check if the letter needs to be counted or not
 for alp in letter:
 # To check the letters are alphabets or not
 if alp in ascii_letters:
 #Converting into lowercase as python is case sensitive
 if alp.lower() in r and alp!=' ':
 r[alp.lower()]+=1
 elif alp.lower() not in r and alp!=' ':
 r[alp.lower()]=1
 # Add or increment the value in the dictionary
 return r

print(count_letters("AaBbCc"))
print(count_letters("Math is fun! 2+2=4"))
print(count_letters("This is a sentence."))
</code></pre>

entityMap|blocks|key|1clvq|text|所以我明白你的问题了，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|ac86n|def+count_letters(text):
++result+=+{}
++text+=+text.lower()
++#+Go+through+each+letter+in+the+text
++for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+letter+in+"abcdefghijklmnopqrstuvwxyz":
++++++#
++++++if+letter+not+in+result:
++++++++result[letter]+=+1
++++++#+Add+or+increment+the+value+in+the+dictionary
++++++else:
++++++++result[letter]+%2B=+1
++return+result

++print(count_letters("AaBbCc"))

++#+Should+be+{'a':+2,+'b':+2,+'c':+2}

++print(count_letters("Math+is+fun!+2%2B2=4"))
++#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+
++1,+'n':+1}

++print(count_letters("This+is+a+sentence."))
++#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+
++1}|code-block|syntax|javascript|d3ffj^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|J|9|@]|A|@]|B|$F|G]]|$2|H|4|-4|6|7|8|K|9|@]|A|@]|B|$]]]]

So I got your question, 

<pre><code>def count_letters(text):
 result = {}
 text = text.lower()
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 if letter in "abcdefghijklmnopqrstuvwxyz":
 #
 if letter not in result:
 result[letter] = 1
 # Add or increment the value in the dictionary
 else:
 result[letter] += 1
 return result

 print(count_letters("AaBbCc"))

 # Should be {'a': 2, 'b': 2, 'c': 2}

 print(count_letters("Math is fun! 2+2=4"))
 # Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 
 1, 'n': 1}

 print(count_letters("This is a sentence."))
 # Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 
 1}
</code></pre>

entityMap|blocks|key|d34ue|text|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+(letter.lower()+not+in+result+)+:
++++++if+not+letter.isalpha():
++++++++continue
++++++result[letter.lower()]+=+0
+++++++++++++#+Add+or+increment+the+value+in+the+dictionary
++++result[letter.lower()]+%2B=+1
++++continue
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|51fd0|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 if (letter.lower() not in result ) :
 if not letter.isalpha():
 continue
 result[letter.lower()] = 0
 # Add or increment the value in the dictionary
 result[letter.lower()] += 1
 continue
 return result

print(count_letters("AaBbCc"))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters("Math is fun! 2+2=4"))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters("This is a sentence."))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|33jfi|text|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++for+letter+in+text.lower():
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+letter.isalpha()+and+letter+not+in+result:
++++#+Add+or+increment+the+value+in+the+dictionary
++++++result[letter]+=+text.lower().count(letter)+
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|10cdq|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text.lower():
 # Check if the letter needs to be counted or not
 if letter.isalpha() and letter not in result:
 # Add or increment the value in the dictionary
 result[letter] = text.lower().count(letter) 
 return result

print(count_letters("AaBbCc"))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters("Math is fun! 2+2=4"))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters("This is a sentence."))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|44jhr|text|def+count_letters(text):
++result+=+{}
++for+letter+in+text:
++++#check+if+it+alphabet+or+something+else
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+letter.isalpha():
++++++result[letter.lower()]=result.get(letter.lower(),0)%2B1
++++#+Add+or+increment+the+value+in+the+dictionary
++return+result|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4kld3|print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}|duvbh|print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}|614r7|print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|cpanh|unstyled^0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|M|9|@]|A|@]|B|$C|D]]|$2|E|4|F|6|7|8|N|9|@]|A|@]|B|$C|D]]|$2|G|4|H|6|7|8|O|9|@]|A|@]|B|$C|D]]|$2|I|4|J|6|7|8|P|9|@]|A|@]|B|$C|D]]|$2|K|4|-4|6|L|8|Q|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 for letter in text:
 #check if it alphabet or something else
 # Check if the letter needs to be counted or not
 if letter.isalpha():
 result[letter.lower()]=result.get(letter.lower(),0)+1
 # Add or increment the value in the dictionary
 return result
</code></pre>
<pre><code>print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}
</code></pre>
<pre><code>print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}
</code></pre>
<pre><code>print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|66ti|text|resultletter.lower()=result.get(letter.lower(),0)%2B1+count_letters(letter.isalpha)：def+text+(Text)：def+text=+{}+#遍历文本中的每个字母：#如果使用def()：def+text()：def#将字典返回结果中的值相加或递增，检查是否需要计算字母|type|unstyled|depth|inlineStyleRanges|entityRanges|data|d9ot7|print(count_letters("AaBbCc"))|1b9rd|应为{'a'：2，'b'：2，'c'：2}|47nv|print(count_letters(“数学很有趣！2%2B2=4"))|91c9u|应为{'m'：1，'a'：1，'t'：1，'h'：1，'i'：1，'s'：1，'f'：1，'u'：1，'n'：1}|7ksd9|print(count_letters(“这是一个句子。”)|5k85h|应为{'t'：2，'h'：1，'i'：2，'s'：3，'a'：1，'e'：3，'n'：2，'c'：1}|endlb^0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|P|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|Q|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|R|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|S|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|T|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|U|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|V|9|@]|A|@]|B|$]]|$2|O|4|-4|6|7|8|W|9|@]|A|@]|B|$]]]]

def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 if letter.isalpha():
 result[letter.lower()]=result.get(letter.lower(),0)+1
 # Add or increment the value in the dictionary
 return result

print(count_letters("AaBbCc"))

<h1>Should be {'a': 2, 'b': 2, 'c': 2}</h1>

print(count_letters("Math is fun! 2+2=4"))

<h1>Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}</h1>

print(count_letters("This is a sentence."))

<h1>Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}</h1>

entityMap|blocks|key|c4ohr|text|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+letter.isalpha():
++++++if+letter+not+in+result:
++++++++result[letter.lower()]+=+1
++++++else:
++++++++result[letter.lower()]+%2B=1
++++#+Add+or+increment+the+value+in+the+dictionary
++++
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|e4oj2|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 if letter.isalpha():
 if letter not in result:
 result[letter.lower()] = 1
 else:
 result[letter.lower()] +=1
 # Add or increment the value in the dictionary
 
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}
</code></pre>

entityMap|blocks|key|7t415|text|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++text=text.lower()
++for+letter+in+text:
++++if+letter+in+'abcdefghijklmnopqrtsuvwxyz':

++++++if+letter+in+result:
++++++++result[letter]%2B=1
++++++
++++++else:
++++++++result[letter]=1
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|91uef|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 text=text.lower()
 for letter in text:
 if letter in 'abcdefghijklmnopqrtsuvwxyz':

 if letter in result:
 result[letter]+=1
 
 else:
 result[letter]=1
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|fu64u|text|".isalpha()“方法非常方便。看看我是如何解决这个问题的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|b2it6|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++
++++if+letter.isalpha()+and+letter+not+in+result:
++++++letter=letter.lower()
++++++result[letter]=1
++++elif+letter.isalpha()==False:
++++++pass
++++else:
++++++result[letter]%2B=1

++++___
++++#+Add+or+increment+the+value+in+the+dictionary
++++___
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|code-block|syntax|javascript|fc48b^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|J|9|@]|A|@]|B|$F|G]]|$2|H|4|-4|6|7|8|K|9|@]|A|@]|B|$]]]]

The &quot;.isalpha()&quot; method comes in very handy. See how I solved it:
<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 
 if letter.isalpha() and letter not in result:
 letter=letter.lower()
 result[letter]=1
 elif letter.isalpha()==False:
 pass
 else:
 result[letter]+=1

 ___
 # Add or increment the value in the dictionary
 ___
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|e6754|text|那么，在第二个评论中，它说你应该：#检查字母是否需要计数|type|unstyled|depth|inlineStyleRanges|entityRanges|data|59bi6|你没有检查这个。仅当字母在名为“result”的字典中时才进行检查，这是添加新字典中不存在的字符所必需的。在这种情况下，您的程序将一个空格作为“字母”。如果我们将'letter‘变量改为'element'，事情会更清楚。|bvfp0|if+letter.isalpha()+==+True:|offset|length|style|CODE|a0cne|您应该使用上面的行来只检查字母。对于输入文本的每个元素，当满足非字母字符(空格、特殊字符数)时，将跳过此块。|f396v|总而言之，你的脚本应该是这样的：|fj973|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+letter.isalpha()+==+True:
++++++if+letter.lower()+not+in+result:
++++++++result[letter.lower()]+=+1
++++#+Add+or+increment+the+value+in+the+dictionary
++++++else:
++++++++result[letter.lower()]+%2B=+1
++++
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|code-block|syntax|javascript|3onk7^0|0|0|0|S|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|U|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|V|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|W|9|@$G|X|H|Y|I|J]]|A|@]|B|$]]|$2|K|4|L|6|7|8|Z|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|10|9|@]|A|@]|B|$]]|$2|O|4|P|6|Q|8|11|9|@]|A|@]|B|$R|S]]|$2|T|4|-4|6|7|8|12|9|@]|A|@]|B|$]]]]

Well, in the second comment it says that you should : # Check if the letter needs to be counted or not
You did not check this. You checked only if the letter is in your dictionary named 'result', which is needed to add characters that don't exist already in the new dictionary. In this case, your program takes a blank space as a &quot;letter&quot;. If we were to change the 'letter' variable as 'element', things would be more clear.
<code>if letter.isalpha() == True:</code>
You should use the above line to check only for the letters. For each element of the input text, this block would be skipped when the a non-letter character is met(blank space, number of special character).
All in all, your script should look like this:
<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 if letter.isalpha() == True:
 if letter.lower() not in result:
 result[letter.lower()] = 1
 # Add or increment the value in the dictionary
 else:
 result[letter.lower()] += 1
 
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|82j4v|text|def+count_letters(text):
++result+=+{}
++text+=+text.lower()
++#+Go+through+each+letter+in+the+text
++for+letter+in+text:
+++
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+letter.isalpha()+:
++++++#+Add+or+increment+the+value+in+the+dictionary
++++++count+=+text.count(letter)
++++++result[letter]+=+count
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|7jsfc|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 text = text.lower()
 # Go through each letter in the text
 for letter in text:
 
 # Check if the letter needs to be counted or not
 if letter.isalpha() :
 # Add or increment the value in the dictionary
 count = text.count(letter)
 result[letter] = count
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|e0nss|text|这就是我所做的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3a0v2|def+count_letters(text):
++++result+=+{}
++#+Go+through+each+letter+in+the+text
++++text=text.lower()
++++for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++++++if+letter.isalpha():
++++#+Add+or+increment+the+value+in+the+dictionary
++++++++++++result[letter]+=+result.get(letter,0)+%2B+1
++++++++else:
++++++++++++pass
++++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}
print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}
print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|code-block|syntax|javascript|410vj^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|J|9|@]|A|@]|B|$F|G]]|$2|H|4|-4|6|7|8|K|9|@]|A|@]|B|$]]]]

This is what i did
<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 text=text.lower()
 for letter in text:
 # Check if the letter needs to be counted or not
 if letter.isalpha():
 # Add or increment the value in the dictionary
 result[letter] = result.get(letter,0) + 1
 else:
 pass
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}
print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}
print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|dovs1|text|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+type(letter)==str:
++++#+Add+or+increment+the+value+in+the+dictionary
+++++if+letter+not+in+result:
+++++++result[letter.lower()]=1
+++++else:
++++++++result[letter.lower()]%2B=1


++++
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1fou|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 if type(letter)==str:
 # Add or increment the value in the dictionary
 if letter not in result:
 result[letter.lower()]=1
 else:
 result[letter.lower()]+=1


 
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|843r1|text|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++for+letter+in+text.lower():
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+letter.isalpha()+and+letter+not+in+result:
++++#+Add+or+increment+the+value+in+the+dictionary
++++++result[letter]+=+text.count(letter)
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|qc5n|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text.lower():
 # Check if the letter needs to be counted or not
 if letter.isalpha() and letter not in result:
 # Add or increment the value in the dictionary
 result[letter] = text.count(letter)
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|64kg5|text|可以使用.isalpha()方法检查字符是否为字母。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|9vcs9|然后使用.get方法返回特定键的值。|fic2a|def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++for+letter+in+text.lower():
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if(letter.isalpha()):
++++++result[letter]+=+result.get(letter,0)%2B1
++++#+Add+or+increment+the+value+in+the+dictionary
++++
++return+result|code-block|syntax|javascript|260tm^0|4|A|0|4|4|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|O|9|@$A|P|B|Q|C|D]]|E|@]|F|$]]|$2|G|4|H|6|7|8|R|9|@$A|S|B|T|C|D]]|E|@]|F|$]]|$2|I|4|J|6|K|8|U|9|@]|E|@]|F|$L|M]]|$2|N|4|-4|6|7|8|V|9|@]|E|@]|F|$]]]]

you can use the <code> .isalpha()</code> method to check if the character is an alphabet letter.
Then use the <code>.get</code> method to return the value from a specific key.
<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text.lower():
 # Check if the letter needs to be counted or not
 if(letter.isalpha()):
 result[letter] = result.get(letter,0)+1
 # Add or increment the value in the dictionary
 
 return result
</code></pre>

entityMap|blocks|key|1b4fh|text|++++def+count_letters(text):
++result+=+{}
++#+Go+through+each+letter+in+the+text
++text=text.casefold()
++for+letter+in+text:
++++#+Check+if+the+letter+needs+to+be+counted+or+not
++++if+(letter.isalpha()):+

++++#+Add+or+increment+the+value+in+the+dictionary
++++++result.update({letter:text.count(letter)})
++return+result

print(count_letters("AaBbCc"))
#+Should+be+{'a':+2,+'b':+2,+'c':+2}

print(count_letters("Math+is+fun!+2%2B2=4"))
#+Should+be+{'m':+1,+'a':+1,+'t':+1,+'h':+1,+'i':+1,+'s':+1,+'f':+1,+'u':+1,+'n':+1}

print(count_letters("This+is+a+sentence."))
#+Should+be+{'t':+2,+'h':+1,+'i':+2,+'s':+3,+'a':+1,+'e':+3,+'n':+2,+'c':+1}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|fkbe3|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code> def count_letters(text):
 result = {}
 # Go through each letter in the text
 text=text.casefold()
 for letter in text:
 # Check if the letter needs to be counted or not
 if (letter.isalpha()): 

 # Add or increment the value in the dictionary
 result.update({letter:text.count(letter)})
 return result

print(count_letters(&quot;AaBbCc&quot;))
# Should be {'a': 2, 'b': 2, 'c': 2}

print(count_letters(&quot;Math is fun! 2+2=4&quot;))
# Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

print(count_letters(&quot;This is a sentence.&quot;))
# Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

entityMap|blocks|key|344q0|text|def+count_letters(text):
++result+=+{}
++for+letter+in+text.lower():
++++if+letter.isalpha():
++++++lettercount+=+text.lower().count(letter)
++++++result[letter]+=+lettercount
++return+result|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|5lf69|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 for letter in text.lower():
 if letter.isalpha():
 lettercount = text.lower().count(letter)
 result[letter] = lettercount
 return result
</code></pre>

entityMap|blocks|key|or7h|text|def+count_letters(text):
++++result+=+{}
++++text+=+text.lower().replace("+","")
++++text+=+text.replace("",+"+").split()
++++dummy+=+[]
++++dummy1+=+""

++++for+x+in+text:+#+remove+non-letter
++++++++if+x.isalpha():
++++++++++++dummy.append(x)
++++++++++++dummy1+=+"".join(dummy)

++++for+letter+in+dummy1:
++++++++if+letter+not+in+result:
++++++++++++result[letter]+=+0
++++++++result[letter]+%2B=+1
++++return+result

print(count_letters("AaBbCc"))
print(count_letters("Math+is+fun!+2%2B2=4"))
print(count_letters("This+is+a+sentence."))|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|p1rh|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 text = text.lower().replace(&quot; &quot;,&quot;&quot;)
 text = text.replace(&quot;&quot;, &quot; &quot;).split()
 dummy = []
 dummy1 = &quot;&quot;

 for x in text: # remove non-letter
 if x.isalpha():
 dummy.append(x)
 dummy1 = &quot;&quot;.join(dummy)

 for letter in dummy1:
 if letter not in result:
 result[letter] = 0
 result[letter] += 1
 return result

print(count_letters(&quot;AaBbCc&quot;))
print(count_letters(&quot;Math is fun! 2+2=4&quot;))
print(count_letters(&quot;This is a sentence.&quot;))
</code></pre>

entityMap|blocks|key|45srh|text|def++count_letters(text):
++++result+=+{}
++++for+letter+in+text.lower():
++++++++if+letter+==+"+"+or+letter.isalpha()+==+False:
++++++++++++continue:
++++++++if+letter+not+in+result:
++++++++++++result[letter]+=+0
++++++++result[letter]+%2B=+1
++++return+result|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|huim|unstyled^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|G|9|@]|A|@]|B|$C|D]]|$2|E|4|-4|6|F|8|H|9|@]|A|@]|B|$]]]]

<pre><code>def count_letters(text):
 result = {}
 for letter in text.lower():
 if letter == &quot; &quot; or letter.isalpha() == False:
 continue:
 if letter not in result:
 result[letter] = 0
 result[letter] += 1
 return result
</code></pre>

Use a dictionary to count the frequency of letters in the input string. Only letters should be counted, not blank spaces, numbers, or punctuation. Upper case should be considered the same as lower case. For example, count_letters("This is a sentence.") should return {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}

<pre><code>def count_letters(text):
 result = {}
 # Go through each letter in the text
 for letter in text:
 # Check if the letter needs to be counted or not
 if letter not in result:
 result[letter.lower()] = 1
 # Add or increment the value in the dictionary
 else:
 result[letter.lower()] += 1
 return result

 print(count_letters("AaBbCc"))
 # Should be {'a': 2, 'b': 2, 'c': 2}

 print(count_letters("Math is fun! 2+2=4"))
 # Should be {'m': 1, 'a': 1, 't': 1, 'h': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1, 'n': 1}

 print(count_letters("This is a sentence."))
 # Should be {'t': 2, 'h': 1, 'i': 2, 's': 3, 'a': 1, 'e': 3, 'n': 2, 'c': 1}
</code></pre>

how to count the frequency of letters in text excluding whitespace and numbers?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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 使用字典统计输入字符串中字母的频率。只应计算字母，而不应计算空格、数字或标点符号。应将大写字母视为与小写字母相同。例如，count_letters(“这是一个句子。”)应返回{'t'：2，'h'：1，'i'：2，'s'：3，'a'：1，'e'：3，'n'：2，'c'：1} def count_letters(text...

问如何统计文本中不含空格和数字的字母出现频率？
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问如何统计文本中不含空格和数字的字母出现频率？EN