I wrote the script to copy a existing shapefile **tc_line** to a new file **tc_pi**, and it ran fine:

    from shapely.geometry import mapping, shape
    import fiona
    
    with fiona.open('tc_line.shp', 'r') as input:
    	schema = input.schema.copy()
        input_crs = input.crs
    	with fiona.open('tc_pi.shp', 'w', 'ESRI Shapefile', schema, input_crs) as output:
    		for elem in input:
    			output.write({'properties':elem['properties'],'geometry': mapping(shape(elem['geometry']))})

Now I want to copy the existing file and add a **new column (type: float) containing "1"** to the attribute table **(I would like the new-added column to be attached to the right of the existing columns in the attribute talle)**, so I edited the code above to this:

    from shapely.geometry import mapping, shape
    import fiona
    
    with fiona.open('tc_line.shp', 'r') as input:
    	schema = input.schema.copy()
    	input_crs = input.crs
    	schema['properties']['pi'] = 'float'
    	with fiona.open('tc_pi.shp', 'w', 'ESRI Shapefile', schema, input_crs) as output:
    		for elem in input:
    			output.write({'properties':elem['properties'],'geometry': mapping(shape(elem['geometry']))})

but error occurred:

    Traceback (most recent call last):
  

    File "C:\Users\Heinz\Desktop\test.py", line 10, in <module>
        output.write({'properties':elem['properties'],'geometry': mapping(shape(elem['geometry']))})
      File "C:\Python27\lib\site-packages\fiona\collection.py", line 333, in write
        self.writerecords([record])
      File "C:\Python27\lib\site-packages\fiona\collection.py", line 327, in writerecords
        self.session.writerecs(records, self)
      File "fiona/ogrext.pyx", line 1024, in fiona.ogrext.WritingSession.writerecs (fiona/ogrext.c:17361)
    ValueError: Record does not match collection schema: [u'cat_', u'value', u'label'] != ['pi', u'label', u'value', u'cat_']

How to solve this and achieve my objective of 'copy the existing file and add a **new column (type: float) containing "1"** to the attribute table of new file'? 

I am working with python 2.7.12, Fiona 1.7.0