Buffering point using PyQGIS?

Question

I have made an attempt to create a buffer around some points useing PyQGIS. However, when running the following code (see below) I receive and IndexError saying that 'list is out of range'.

What might be the issue?

layerName = "C:/Users/Anna Nilsson/Desktop/AIRPOLIM-ES/GIS data/Kenya/cpp_KE_meters.gpkg"
iface.addVectorLayer(layerName,"coal plants","ogr")
outFn = "C:/Users/Anna Nilsson/Desktop/buffer1.shp"
bufferDist = 100000 #in map units

layers = QgsProject.instance().mapLayersByName(layerName)
layers = layers[0] #buffered layer is the first layer in layers list

fields = layers.fields()
feats = layers.getFeatures()

writer = QgsVectorFileWriter(outFn,'UTF-8',fields,QgsWkbTypes.Point,layers.sourceCrs(),'ESRI Shapefile')

for feat in feats: 
    geom = feat.geometry()
    buff = geom.buffer(bufferDist,5)
    feat.setGeometry(buff)
    writer.addFeature(feat)

iface.addVectorLayer(outFn, '', 'ogr')

del(writer)

Error message:

Traceback (most recent call last):
  File "C:\PROGRA~1\QGIS3~1.4\apps\Python37\lib\code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
  File "<string>", line 19, in <module>
IndexError: list index out of range

Answer 1

try using the layer name instead of its path

layers = QgsProject.instance().mapLayersByName("coal plants")