ENH: allow to define datatypes instead of converters

Summary

Previously, converters was the only argument of the TableImporter that defined the columns that should be treated. This implied the problem that supplying colname: int would prevent the very useful parsing of NaNs done by pandas by default.

Now, there is the additional argument datatypes where columns can be supplied if no special converter function is needed (i.e. str, int, etc).

Focus

TableImporter

Test Environment

unitttest

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• All automated tests pass
• Reference related Issues
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  • Intent of new code
  • Problems with old code
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• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md
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src/caosadvancedtools/table_importer.py

@@ -186,7 +186,8 @@ def string_in_list(val, options, ignore_case=True):
 
 
 class TableImporter(object):
-    def __init__(self, converters, obligatory_columns=None, unique_keys=None):
+    def __init__(self, converters, obligatory_columns=None, unique_keys=None,
+                 datatypes=None):
         """
         converters: dict with column names as keys and converter functions as
                     values
@@ -200,14 +201,27 @@ class TableImporter(object):
         unique_columns : list of column names that in
                             combination must be unique; i.e. each row has a
                             unique combination of values in those columns.
+        datatypes: dict with column names as keys and datatypes as values
+                   All non-null values will be checked whether they have the
+                   provided datatype.
+                   This dict also defines what columns are required to exist
+                   throught the existing keys.
         """
+
+        if converters is None:
+            converters = {}
+
+        if datatypes is None:
+            datatypes = {}
+
         self.sup = SuppressKnown()
-        self.required_columns = list(converters.keys())
+        self.required_columns = list(converters.keys())+list(datatypes.keys())
         self.obligatory_columns = ([]
                                    if obligatory_columns is None
                                    else obligatory_columns)
         self.unique_keys = [] if unique_keys is None else unique_keys
         self.converters = converters
+        self.datatypes = datatypes
 
     def read_file(self, filename, **kwargs):
         raise NotImplementedError()
@@ -265,6 +279,22 @@ class TableImporter(object):
 
         return df
 
+    def check_datatype(self, df, filename=None):
+        """
+        Check for each column whether non-null fields are have the correct
+        datatype.
+        """
+
+        for key, datatype in self.datatypes.items():
+            for idx, val in df.loc[pd.notnull(df.loc[:, key]), key].iteritems():
+                if not isinstance(val, datatype):
+                    raise DataInconsistencyError(
+                        "In row no. {rn} and column {c} of file '{fi}' the "
+                        "datatype was {was} but it should be "
+                        "{expected}".format(rn=idx, c=key, fi=filename,
+                                            was=type(val), expected=datatype)
+                    )
+
     def check_missing(self, df, filename=None):
         """
         Check in each row whether obligatory fields are empty or null.
@@ -309,6 +339,7 @@ class TableImporter(object):
     def check_dataframe(self, df, filename):
         self.check_columns(df, filename=filename)
         df = self.check_missing(df, filename=filename)
+        self.check_datatype(df, filename=filename)
 
         if len(self.unique_keys) > 0:
             df = self.check_unique(df, filename=filename)