如何检查 dataframe pandas 中是否不存在列列表

Question

I have a dataframe (df) and list (l) containing a list of column names. df:

Col_A	Col_B	Col_D	Col_G
AA	12	Q	no
BB	23	W	yes
WW	44		yes

l = ['Col_A', 'Col_B', 'Col_C', 'Col_D', 'Col_E', 'Col_F', 'Col_G']

I would like to print the column names that are not present in the df.

Desired output:

['Col_C', 'Col_E', 'Col_F']

What I tried so far:

if l not in df.columns:
    print(l)

I get an error TypeError: unhashable type: 'list'

Answer 1

You can use list comprehension for this:

[i for i in l if i not in df.columns]

This goes through every element in l ( i ) and if it is not in the columns of df, it will add it to a new list. Output:

['Col_C', 'Col_E', 'Col_F']

Answer 2

Use numpy.setdiff1d :

L = np.setdiff1d(l, df.columns).tolist()

Or Index.difference :

L = pd.Index(l).difference(df.columns).tolist()

Or list comprehension with not in :

L = [x for x in l if x not in df.columns]

---

print (L)
['Col_C', 'Col_E', 'Col_F']

Answer 3

You have to loop over the list l .

Like:

for item in l:
  if item not in df.columns:
    print(item) 

Answer 4

You can use set difference:

list(set(l).difference(df.columns))

or

list(set(l) - set(df.columns))