# Calculate probability of word occurence

I am pretty new in Python and I am not sure if I did everything right in my program. May someone to check it, please. Thank you!

1. First of all, I have a text file, for example, abc.txt.
2. I have to create a dictionary and for this, I have to split the sentences into a list of words and convert each word to lowercase.
3. Then I have to assign a counter to each word in my dictionary and increment it every time when I meet this word in sentence one more time.
4. Finally, I have to divide the word count by sum of all counts (prob = count(word) / sum(count of all words in dict) and write this probability into new file called x.txt.

Here is what I got so far:

import sys
filename = 'abc.txt'
new_dict ={}
total_count = 0
with open(filename, "r") as fp:
for line in fp:
words = line.split()

for word in words:
word = word.lower()

if not word in new_dict:
new_dict[word] = 1
else:
new_dict[word] +=1
total_count +=1
probab = new_dict[word]/ total_count
print(probab)
fp.close()
output_file = 'x.txt'
with open(output_file, "w") as fs:
fs.write(str(probab))
fs.close()


and my output is 0.0006865437426441742

• and my input is 0.0006865437426441742 Are you sure this is your input?
– yuri
Jun 30 '17 at 7:08
• You're only adding one word from each line to the dict. You may want to move the if-else blocks under the for-loop. Please fix issues with your code first. Jun 30 '17 at 7:26
• Doing just this won't be too effective. As you have mentioned that the file contains sentences so you might miss the same word a '.' or a ',' or other characters. eg."i am going" will give you ['i,','am','going'] and " i am going." will give you ['i', 'am','going.']. Jun 30 '17 at 7:35

## 1 Answer

I apologize for updating my answer multiple times. I shouldn't upload my answer when I'm tired.

I'm going to ignore the running time complexity to avoid confusing you.

If you want to know, this will run in O(n^2) time. This can be simplified to O(n log n) time using a tree, but using and explaining a tree might confuse a beginner.

The simplest way to do and undertand this is as follows:

    # you don't need "import os" in this case.
new_dict = {}

# This is to open the file to get the count of all words:
filename = 'abc.txt'
with open(filename, "r") as fp:
for line in fp:
# For this to work, make sure the words don't end with any punctuation.
# If any words end with a punctuation, take a look into re.sub()
words = line.split()

for word in words:
word = word.lower()

if word not in new_dict:
new_dict[word] = 1
else:
new_dict[word] += 1

# This is to calculate the count of all words:
total_words = sum(new_dict.values())

# This is used to get the probability of each word.
output_file = 'x.txt'
with open(output_file, "w") as fs:
# The dictionary is set as: {dictionary_name[key] : value}
for key, value in sorted(new_dict.items()):
probability = value / total_words
fs.write(key + ": " + str(probability) + "\n")


• ### Using for x_variable in collection_variable

When you are using for x_variable in collection_variable, you need to make sure any code using the x_variable resides inside of the for each loop. In this case, I pushed anything that uses word to make sure the word variable is accessible because you are calling it from inside the for word in words iterator.

• ### When to call file.close()

When opening files with the with open(...) function, you don't need to explicitly close it. You can just leave the with open code block and the garbage collector will know you are done with that file. However, if you do open(...) without the with operator, then yeah, you need to call fs.close()

• ### How sorted(variable) works

With simple data types like string, int, float, tuple, list, dictionary, they already include comparison functions, so you can use sorted(variable) to sort them. However, if you have your own data type or object, you need to define the comparison functions for the sorted() to work. Read more about sorted(variable) on Python docs

Hope this helps :)

• The last version what I got was: gist.github.com/anonymous/f0179a6549b87667c3448fa75d12bad1 Jul 1 '17 at 5:40
• @Marishka33, I uploaded [hopefully] my last answer update. I just want to make sure it works for you. Jul 1 '17 at 19:05