title: How to transform JSON strings in columns of dataframe in PySpark?
body: <p>I have a pyspark dataframe as shown below</p>
  
  <pre><code>+--------------------+---+
  |            _c0|_c1|
  +--------------------+---+
  |{"object":"F...|  0|
  |{"object":"F...|  1|
  |{"object":"F...|  2|
  |{"object":"E...|  3|
  |{"object":"F...|  4|
  |{"object":"F...|  5|
  |{"object":"F...|  6|
  |{"object":"S...|  7|
  |{"object":"F...|  8|
  </code></pre>
  
  <p>The column <code>_c0</code> contains a string in dictionary form. </p>
  
  <pre><code>'{"object":"F","time":"2019-07-18T15:08:16.143Z","values":[0.22124142944812775,0.2147877812385559,0.16713131964206696,0.3102800250053406,0.31872493028640747,0.3366488814353943,0.25324496626853943,0.14537988603115082,0.12684473395347595,0.13864757120609283,0.15222792327404022,0.238663449883461,0.22896413505077362,0.237777978181839]}'
  </code></pre>
  
  <p>How can I  convert the above string to a dictionary form and fetch each key value pair and store it to a variables? I don't want to convert it to pandas as it is expensive.</p>