如何根据 pandas Dataframe 的条件打印值？

Question

I'm new to pandas dataframe and python. Currently, I have a pandas dataframe which I'd like to print the values based on conditions set.

My df looks like this:

ID     Name    Price
1      Apple     1
2      Orange    0.5
3      Pear      0.7

I'd like to code it such that when I ask the user to input the ID, it will return the price. For example, if the user input 2, it should return 0.5.

inputid = input("Please input ID: ")

What should I do next to get return Price from df based on the input?

Answer 1

One of possible solutions:

1. Set ID column in df as its index:

    df.set_index('ID', inplace=True)

2. Define the following function:

    def getPrice(): inputid = input("Please input ID: ") try: return df.loc[int(inputid), 'Price'] except: return 'No such ID'

Then when you call it, executing getPrice() :

• An input prompt is displayed.
• The user enters the ID.
• Within try block this function attempts to:
  • convert inputid to int (the index contains int values, but inputid is a string ), so one cause of error can be that the user just pressed Enter without entering any value,
  • even if the user entered a number, it is possible that df does not contain such ID (the second cause of error).
• If everything so far is OK, the function returns the price of interest.
• But if any error occurred, the result is an error message.

Answer 2

The Pandas documentation is very good and will cover everything you need.

https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html

Let's call your DataFrame price_df , depending on whether your ID column is set as the index of the dataframe or not.

If it is:

print(price_df.loc[inputid, "Price"])

If it isn't:

print(price_df[price_df["ID"] == inputid]["Price"])

The .loc method is the primary way of accessing data from a DataFrame.

Answer 3

Here is a working solution.

df = pd.DataFrame({'ID' : (1, 2,3),
                  'Name':('Apple', 'Orange', 'Pear'),
                  'Price': (1, 0.5, 0.7)})
df
    ID  Name    Price
0   1   Apple   1.0
1   2   Orange  0.5
2   3   Pear    0.7

userin = input("Please input ID: ")
userin
`1`

df.loc[df['ID'] == float(userin)]

    ID  Name    Price
0   1   Apple   1.0

You need to change the user input to float or int for pandas to read.

Answer 4

You can try:

userin = input("input ID: ")

print("The price for the ID is- ",df[df.ID==float(userin)].Price.values[0])