CODEWITHSUNDEEP
pythonarcgisutcarcpylidar
Garret
Garret

Reputation: 1

ValueError: not enough values to unpack (expected 4, got 3), gps time to UTC

Trying to convert GPS times to a date and time of day in UTC. Inputs are space separated stream of x y seconds and output is a stream of x y z date time

This was designed to work with lidar data and the input may have come from a command like 'las2txt -parse xyt ...'.

import datetime
import fileinput

#number of seconds between the start of unix time (Jan 1, 1970) and gps time (Jan 6, 1980)
offset = 315964800


def countleaps(gpsTime):
  """Count number of leap seconds that have passed."""

  # a tuple of the gps times where leap seconds were added
  leaps = (
    46828800, 78364801, 109900802, 173059203, 252028804,
    315187205, 346723206, 393984007, 425520008, 457056009,
    504489610, 551750411, 599184012, 820108813, 914803214, 
    1025136015
    )

  nleaps = 0
  for leap in leaps:  
    if gpsTime >= leap:
       nleaps += 1
  
  return nleaps

if __name__ == '__main__':
  for line in fileinput.input(r'E:\LiDAR\Staging\GW_Workspace\Beaverhead_Reports\BH_0001.txt'):
    xvalue, yvalue, zvalue, timevalue=line.split(' ')[:4]
    gpstime=float(timevalue)
    gpstime += 1e9; # unadjusted GPS time
    unixtime = gpstime + offset - countleaps(gpstime);
    datetimestr = datetime.datetime.fromtimestamp(unixtime).strftime('%Y-%m-%d %H:%M:%S')
    
    print xvalue, yvalue, zvalue, datetimestr

Error:

Traceback (most recent call last):
  File "C:\Users\cwc051\PycharmProjects\sandbox\.venv\Sanbox_script.py", line 29, in <module>
    xvalue, yvalue, zvalue, timevalue=line.split(' ') [:4]
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: not enough values to unpack (expected 4, got 3)

Upvotes: 0

Views: 56

Answers (2)

Barmar
Barmar

Reputation: 782166

If a line doesn't have at least 4 fields, you can't assign them to 4 variables. You need to check for that and take appropriate action:

fields = line.split(' ')
if len(fields) >= 4:
    xvalue, yvalue, zvalue, timevalue=fields[:4]
else:
    # assign variables some other way

or you could simply skip those lines:

if len(fields) < 4:
    continue

Upvotes: 0

Bill Horvath
Bill Horvath

Reputation: 1717

Your problem is here: timevalue=line.split(' ')[:4]

You're telling python "Assign values to these four variables using the first four elements in the array resulting from the split operation", but based on the contents of the error you're receiving, at least one line only has two spaces in it, so the array has only three elements, so there is no fourth element to assign to the timevalue variable.

Upvotes: 1

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