Multiplie Specific row with specific condition pandas-CodePudding

I want to multiple a column in pandas and replace the old value by the value computed.

Example :

EURUSD = 2
print(df)

           Instrument      Price,
  1         BTC/EUR        40000
  2         ETH/EUR        3000         
  3         SOL/USD        3200
  4         ADA/EUR        2.2 
  5         DOT/USD        29

)

If the instrument ends by "EUR", I would like to multiply the price by the exchange rate EURUSD to convert the price in USD.

The result would be :

print(df)

           Instrument      Price,
  1         BTC/EUR        80000
  2         ETH/EUR        6000         
  3         SOL/USD        3200
  4         ADA/EUR        4.4
  5         DOT/USD        29

)

I tried the following code :

df.loc[df["Instrument"].str[-3:] == "EUR",df["Price"]]=df["Price"]*EURUSD

CodePudding user response：

You can use np.where with Series.str.contains:

In [167]: import numpy as np

# Check whether the 'Instrument' value contains 'EUR', if TRUE then PRICE * 2, otherwise leave PRICE as is. 
In [168]: df['Price'] = np.where(df.Instrument.str.contains('EUR'), df.Price.mul(2), df.Price)

In [169]: df
Out[169]: 
  Instrument    Price
1    BTC/EUR  80000.0
2    ETH/EUR   6000.0
3    SOL/USD   3200.0
4    ADA/EUR      4.4
5    DOT/USD     29.0

CodePudding user response：

Pass correct loc format

df.loc[df["Instrument"].str[-3:] == "EUR","Price"] = df["Price"]*EURUSD
df
Out[419]: 
  Instrument    Price
1    BTC/EUR  80000.0
2    ETH/EUR   6000.0
3    SOL/USD   3200.0
4    ADA/EUR      4.4
5    DOT/USD     29.0