Editing shapefile adding fields with values with pyshp

Question

I'm trying to add some fields to a shapefile using pyshp. The code I have to far is:

import shapefile
# Read in our existing shapefile
r = shapefile.Reader(r"C:\...\Edit_SHP\TracksLines.shp")
# Create a new shapefile
w = shapefile.Writer(r"C:\...\Edit_SHP\TracksLines_edited.shp")
# Copy over the existing fields
w.fields = list(r.fields)
# Copy over the records
for shaperec in r.iterShapeRecords():
 w.record(*shaperec.record)
 w.shape(shaperec.shape)
w.field('test')

The issue is that when I try to add a new field all the records already present on the shape are messed up.

How can I keep the same numbers of records, when adding new fields?

Original attribute table

Edited shpfile

• Taras: Maybe this can help you: geospatialpython.com/2013/04/…
• user179413: Just tried, but it doesn't work, or maybe I'm just doing something wrong.
• gene: look at the answers in Updating Attributes using Pyshp