Pandas lambda function syntax error (with dictionary)

Question

I use lambda functions in Python a lot. All of a sudden, I cannot figure out why is there a syntax error message for this:

table['sp1 name'] = table['sp1'].apply(lambda x: sp1_new_dict[x] if x in sp1_new_dict.keys())

Any ideas? Thanks!

simply, sp1_new_dict[x] if x in sp1_new_dict.keys() is not a valid expression, thus it cannot go there, hence the SyntaxError — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Nov 29, 2022 at 17:07
lambda function must have a return value for every valid input hence the else expression must be provided — user19077881
– user19077881, Commented Nov 29, 2022 at 17:12

C.Nivs · Accepted Answer · 2022-11-29 17:08:34Z

2

You need an else. Boiling down your error:

x = 1 if True

  File "<stdin>", line 1
    x = 1 if True
                 ^
SyntaxError: invalid syntax


# No error here
x = 1 if True else 2

Since you are using a dictionary, maybe use dict.get:

table['sp1 name'] = table['sp1'].apply(lambda x: sp1_new_dict.get(x))

Which returns None if the key isn't present

answered Nov 29, 2022 at 17:08

C.Nivs

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