将所有行更改为与第一行具有相同的数据，但一列除外

Question

I have a dataframe called df like so:

x1  x2  x3  x4  x5  x6  x7  x8
1   0   5   6   10  11  56  7
67  10  4   87  2   34  22  12
44  16  9   9   5   11  56  7
99  82  10  6   87  9   5   8
5   54  66  7   36  3   2   7

I want to change every row to be like row 1 except for the column x1.

My expected output would be:

x1  x2  x3  x4  x5  x6  x7  x8
1   0   5   6   10  11  56  7
67  0   5   6   10  11  56  7
44  0   5   6   10  11  56  7
99  0   5   6   10  11  56  7
5   0   5   6   10  11  56  7

How can i do this in pandas?

Answer 1

df.loc[:, "x2":] = df.loc[0, "x2":].values
print(df)

Prints:

   x1  x2  x3  x4  x5  x6  x7  x8
0   1   0   5   6  10  11  56   7
1  67   0   5   6  10  11  56   7
2  44   0   5   6  10  11  56   7
3  99   0   5   6  10  11  56   7
4   5   0   5   6  10  11  56   7

---

EDIT: For column x4 :

x4 = df["x4"].copy()
df.loc[:, :] = df.loc[0, :].values
df["x4"] = x4
print(df)

Prints:

   x1  x2  x3  x4  x5  x6  x7  x8
0   1   0   5   6  10  11  56   7
1   1   0   5  87  10  11  56   7
2   1   0   5   9  10  11  56   7
3   1   0   5   6  10  11  56   7
4   1   0   5   7  10  11  56   7

Answer 2

df.iloc[1:,1:]=np.nan#slice rows and columns to eliminate the first row and column and make them nan
df=df.ffill().astype(int)#forward fill the slice
print(df)

    x1  x2  x3  x4  x5  x6  x7  x8
0   1   0   5   6  10  11  56   7
1  67   0   5   6  10  11  56   7
2  44   0   5   6  10  11  56   7
3  99   0   5   6  10  11  56   7
4   5   0   5   6  10  11  56   7

Answer 3

With df.assign :

cols = ['x1'] #change list as required ex: cols = ['x1','x2']
out = df.assign(**df.drop(cols,1).iloc[0])

---

print(out)

   x1  x2  x3  x4  x5  x6  x7  x8
0   1   0   5   6  10  11  56   7
1  67   0   5   6  10  11  56   7
2  44   0   5   6  10  11  56   7
3  99   0   5   6  10  11  56   7
4   5   0   5   6  10  11  56   7

Answer 4

Use df.iloc with row range 1: assigned with row 0 . All operating on column range 1:

df.iloc[1:, 1:] = df.iloc[0, 1:]



print(df)

   x1  x2  x3  x4  x5  x6  x7  x8
0   1   0   5   6  10  11  56   7
1  67   0   5   6  10  11  56   7
2  44   0   5   6  10  11  56   7
3  99   0   5   6  10  11  56   7
4   5   0   5   6  10  11  56   7