According to Wilber's October 1940 World War II draft registration, he was living at 20 Shaw Street in North Weymouth. This would be in ED 11-294 and should be on sheet 1B.
By looking at Google maps, I see that 30 Shaw is part of a 2 family home of 28-30 Shaw. The census taker does appear to have taken the listing for the family in #28 (Charles W Overtt) but not for the family in #30.
It is possible that the Purdy's move to #30 after the census and before October but I have not found evidence of them anywhere else.
World War II Draft Registration
16 Oct 1940
Weymouth, Norfolk County, Massachusetts
Ancestry.com. U.S., World War II Draft Cards Young Men, 1940-1947
Name Wilbur Charles Purdy
Gender Male
Race White
Age 34
Birth Date 25 Dec 1905
Birth Place West Newton, Massachusetts
Residence Place Weymouth, Norfolk, Massachusetts
Registration Date 16 Oct 1940
Registration Place Weymouth, Massachusetts, USA
Employer Quincy Adams York Yard
Height 6ft 2"
Weight 168
Complexion Light
Hair Color Brown
Eye Color Blue
Next of Kin Mrs Phyllis M Purdy
1950 Census
4 Apr 1950
Weymouth, Norfolk County, Massachusetts
ED 11-371, sheets 5-6
19 Hill Street
Purdy, Wilbur C Head W M 44 Md Mass House Painter - Painting Contractor
----- sheet 6 -----
Purdy, Phyllis M Wife W F 36 Md Mass
---, John W. Son W M 16 S Mass
---, Jane Dau W F 14 S Mass
---, David L. Son W M 8 S Mass
---, Bruce C. Son W M 7 S Mass
Died
7 Mar 1951
Weymouth, Norfolk County, Massachusetts
Buried
Aft 7 Mar 1951
Washington Street Cemetery, Norwell, Plymouth County, Massachusetts
Phyllis Margarite Keene, b. 19 Jan 1914, Weymouth, Norfolk County, Massachusetts , d. 2 Dec 2006, Weymouth, Norfolk County, Massachusetts (Age 92 years)
Married
1932
Marshfield, Plymouth County, Massachusetts
Ancestry.com. Massachusetts, U.S., Marriage Index, 1901-1955 and 1966-1970
Name: Wilbur Charles Purdy
Marriage Year: 1932
Marriage Place: Marshfield, Massachusetts, USA
Index Volume Number: 122
Reference Number: F63.M36 v.112
Wilbur Charles Purdy Marshfield 1932 Vol. 38 p. 265
" Scituate 1932 50 373
Name: Phillis Keene
Marriage Year: 1932
Marriage Place: Scituate, Massachusetts, USA
Index Volume Number: 110
Reference Number: F63.M36 v.110
1. John Wilder "Jack" Purdy, b. 23 Apr 1933, Marshfield, Plymouth County, Massachusetts , d. 7 Jan 2020, Weymouth, Norfolk County, Massachusetts (Age 86 years)