OSGB36 to wgs84

# fixed version of http://altons.github.io/python/2012/12/01/converting-northing-and-easting-to-latitude-and-longitude/
# - filenames
# - data type (pyproj transform doesn't like pandas series) 
import os
import pandas as pd
import pyproj
import re

listfiles = os.listdir("codepo/Data/CSV")
pieces = []
columns = ['pstcode','positional_quality_indicator','eastings','northings','country_code','nhs_regional_ha_code',
           'nhs_ha_code','admin_county_code','admin_district_code','admin_ward_code']
print listfiles
for f in listfiles:
  path = "codepo/Data/CSV/%s" % f
  frame=pd.read_csv(path, names = columns)
  frame['filename']=f
  pieces.append(frame)

postcodes = pd.concat(pieces, ignore_index=True)

sample = postcodes

def proj_transform(df):
    #bng = pyproj.Proj(init='epsg:27700')
    bng = pyproj.Proj("+init=EPSG:27700")
    #wgs84 = pyproj.Proj(init='epsg:4326')
    wgs84 = pyproj.Proj("+init=EPSG:4326")
    lats = pd.Series()
    lons = pd.Series()
    for idx, val in enumerate(df['eastings']):
      lon, lat = pyproj.transform(bng,wgs84,df['eastings'][idx], df['northings'][idx])
      lats.set_value(idx, lat)
      lons.set_value(idx, lon)
    df['lat'] = lats
    df['lon'] = lons
    return df

sample2 = proj_transform(sample)
sample2.to_csv('uk-postcodes-latlng.csv',index=False)

Resolved through stack overflow, I had some NaN values in the data. More reading on that here for others reference.

I also had an issue with RuntimeError: non-convergent inverse meridional dist

Resolved by code below;

def proj_transform2(df): 
    bng = pyproj.Proj("+init=EPSG:27700") 
    wgs84 = pyproj.Proj("+init=EPSG:4326") 
    arr = map(lambda x: pyproj.transform(bng, wgs84, x[0], x[1]), 
    zip(df['eastings'], df['northings'])) 
    lons, lats = map(array, zip(*arr)) 
    df['lat'] = lats 
    df['lon'] = lons
    return df