can not convert column type from object to str in python dataframe
<p>i have downloaded a csv file, and then read it to python dataframe, now all 4 columns all have object type, i want to convert them to str type, </p>

<p><a href="https://i.stack.imgur.com/WeVYV.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/WeVYV.jpg" alt="enter image description here"></a></p>

<p>and now the result of dtypes is as follows:</p>

<pre><code>Name                      object
Position Title            object
Department                object
Employee Annual Salary    object
dtype: object
</code></pre>

<p>i try to change the type using the following methods:</p>

<pre><code>path['Employee Annual Salary'] = path['Employee Annual Salary'].astype(str)
</code></pre>

<p>but dtypes still return type object,
and i also try to provide the column type when reading csv, </p>

<pre><code>path = pd.read_csv("C:\\Users\\IBM_ADMIN\\Desktop\\ml-1m\\city-of-chicago-salaries.csv",dtype={'Employee Annual Salary':str})
</code></pre>

<p>or </p>

<pre><code>path = pd.read_csv("C:\\Users\\IBM_ADMIN\\Desktop\\ml-1m\\city-of-chicago-salaries.csv",dtype=str)
</code></pre>

<p>but still do not work, 
want to know how to change column type from object to str,</p>