How to count No. of cells with None value (string data-type) in all columns of a Spark DataFrame?

Question

I have a large dataset and some columns have String data-type. Because of typo mistake, some of the cells have None values but written in different styles (with small or capital letters, with or without space, with or without bracket, etc).

I want to count the No. of all those values (excluding Null values) in all columns. A sample dataset is below:

data = [("A", "None", 1), \
    ("A", "(None)", 2), \
    ("[None", "none", 3), \
    ("(none]", "[None]", 4), \
    ("A", "(none)", 5), \
    ("A", "(none", 6), \
    ("A", "none  ", 7), \
    (" NOne  ", None, None), \
  ]

# Create DataFrame
columns= ["col_1", "col_2", "Number"]
df = spark.createDataFrame(data = data, schema = columns)

The expected result is:

{'col_1': 3, 'col_2': 7, 'Number': 0}

Any idea how to do that by PySpark?

Answer 1

The logic is:

• Use regex to remove all kinds of opening brackets and closing brackets from start and end of the column value.
• Trim extra spaces, convert to lower and compare to "none".
• Count the filtered records for each column.

count_result = {}
for c in df.columns:
  count_result[c] = df.select(c).filter(F.lower(F.trim(F.regexp_replace(c, r"(?:^\[|^\(|^\<|^\{|\]$|\)$|\>$|\}$)", ""))) == "none") \
               .count()
  
print(count_result)

Output:

{'col_1': 3, 'col_2': 7, 'Number': 0}