how to replace few values with nan in column code example

Example 1: replace "-" for nan in dataframe

df.replace(np.nan,0)

Example 2: python dataframe replace nan with 0

In [7]: df
Out[7]: 
          0         1
0       NaN       NaN
1 -0.494375  0.570994
2       NaN       NaN
3  1.876360 -0.229738
4       NaN       NaN

In [8]: df.fillna(0)
Out[8]: 
          0         1
0  0.000000  0.000000
1 -0.494375  0.570994
2  0.000000  0.000000
3  1.876360 -0.229738
4  0.000000  0.000000

Example 3: replace all nan values in dataframe

# Replacing all nan values with 0 in Dataframe
df = df.fillna(0)