# Code error from exercise in module 5

**URL:** <https://forum.codewithmosh.com/t/code-error-from-exercise-in-module-5/7561>\
**Category:** Python\
**Created:** [September 26, 2021, 3:11pm UTC](https://forum.codewithmosh.com/t/code-error-from-exercise-in-module-5/7561 "2021-09-26T15:11:15Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![paulcoder](https://avatars.discourse-cdn.com/v4/letter/p/b77776/32.png) [@paulcoder](https://forum.codewithmosh.com/u/paulcoder)\
**Post date:** [September 26, 2021, 3:11pm UTC](https://forum.codewithmosh.com/t/code-error-from-exercise-in-module-5/7561/1 "2021-09-26T15:11:15Z")

</div>

Hi all,

I am doing Mosh’s Python course and completing the exercise at the end of module 5. I am copying his code exactly as Mosh is and I keep getting this error. Anyone know why? Thanks in advance.

```auto
...line 5, in <module>
    if char in char_frequency:
TypeError: argument of type 'int' is not iterable

```

The code I am inputting is:

```auto
char_frequency = {}
for char in sentence:
    if char in char_frequency:
        char_frequency[char] += 1
    else:
        char_frequency = 1
```

---

<div class="post-metadata">

**Author:** ![eelsholz](https://avatars.discourse-cdn.com/v4/letter/e/439d5e/32.png) [@eelsholz](https://forum.codewithmosh.com/u/eelsholz)\
**Post date:** [September 27, 2021, 1:06am UTC](https://forum.codewithmosh.com/t/code-error-from-exercise-in-module-5/7561/2 "2021-09-27T01:06:42Z")

</div>

Look closely at your last line.

```auto
if char in char_frequency:
    char_frequency[char] += 1
else:
    char_frequency[char] = 1

```

---

<div class="post-metadata">

**Author:** ![paulcoder](https://avatars.discourse-cdn.com/v4/letter/p/b77776/32.png) [@paulcoder](https://forum.codewithmosh.com/u/paulcoder)\
**Post date:** [September 27, 2021, 2:26am UTC](https://forum.codewithmosh.com/t/code-error-from-exercise-in-module-5/7561/3 "2021-09-27T02:26:14Z")

</div>

Ahh cheers! 😅 Was missing the [char]. Are you familiar with this problem? I actually solved it a totally different way. Mosh went and made “sentence” into a dictionary. Here is what I did:

```auto
list = []
for element in sentence:
    list.append(element)
x = max(list,key=list.count)
print(x)

```

I used an empty list and appended it with ‘max’. I can see the different procedures of these, but I am still unsure of the implications beyond this. Like what is the difference between doing what Mosh did (i.e. using a dictionary) and what I did (appending an empty list) ??

---

<div class="post-metadata">

**Author:** ![eelsholz](https://avatars.discourse-cdn.com/v4/letter/e/439d5e/32.png) [@eelsholz](https://forum.codewithmosh.com/u/eelsholz)\
**Post date:** [October 11, 2021, 1:13am UTC](https://forum.codewithmosh.com/t/code-error-from-exercise-in-module-5/7561/4 "2021-10-11T01:13:44Z")

</div>

One difference between the two approaches is performance.

In the Mosh approach we:

- Iterate through the sentence once to build up the `char_frequency` dictionary.
- Iterate through the `char_frequency` dictionary once to find out which character was the most  
frequent.

In the list approach we:

- Iterate through the sentence once to build up the list.
- Iterate through the list once to call the `list.count` function for each item, which in turn must…
  - Iterate through the list to calculate the count of the item.

So with the list approach, if the sentence is ten characters long, then the `list.count` function will be run 10 times and each time must examine 10 items, i.e. in total it must examine 10 x 10 = 100 items. In other words, if the list is n items long, then we need to examine n x n items i.e. n2 items, and so the performance of this approach is proportional to the square of n. Compare to the Mosh approach, which is proportional to n i.e. as n increases, performance decreases, but only linearly, not squared. As n2 is usually larger and sometimes much larger than n, the performance of n2 algorithms is usually worse than the performance of n algorithms.

Whether the performance difference really matters here is another question.