def _depending_columns(self, ds):
'''Find all columns that this selection depends on for df ds'''
depending = set()
for expression in self.expressions:
expression = ds._expr(expression) # make sure it is an expression
depending |= expression.variables()
if self.previous_selection:
depending |= self.previous_selection._depending_columns(ds)
return depending
def _depending_columns(self, ds):
'''Find all columns that this selection depends on for df ds'''
depending = set()
for expression in self.expressions:
expression = ds._expr(expression) # make sure it is an expression
depending |= expression.variables()
if self.previous_selection:
depending |= self.previous_selection._depending_columns(ds)
return depending
