Python Challenge level 2

http://www.pythonchallenge.com/pc/def/ocr.html

- find the mess message in the page source (commend), copy the content and save it as a file

- "find rare characters in the mess below", so find the letter frequency of this message

f = open("filename.txt", "r")
dict = {}
for line in f:
 line_list = list(line)
 for i in line_list:
  dict[i] = (dict[i]+1) if (i in dict) else 1

- the result shows:

:1219

!: 6079

#: 6115

%: 6104

$: 6046

&: 6043

): 6186

(: 6154

+: 6066

*: 6034

@: 6157

[: 6108

]: 6152

_: 6112

^: 6030

a: 1

e: 1

i: 1

l: 1

q: 1

u: 1

t: 1

y: 1

{: 6046

}: 6105

- find that some letters only show once (so called rare characters), but still don't know the order, find the order

ans = ''
for line in f:
 line_list = list(line)
 for i in line_list:
  if dict[i] == 1: ans = ans + i
print ans

- the answer is "equality"
- it's occurred to me that I should use regular expression ;(  Never mind! It will be used in the next level.