Как найти индекс строки по значению pandas

У меня есть массив. Я хочу получить индекс строки, в котором находится искомое значение.

Я обращаюсь к таблице, чтобы вернуть значение индекса. Например хочу знать какой индекс имеет строка, где находить значение “Сумма” равное 2287.6. Оно должно мне возвращать 5.

ind = df[df['Сумма'] == 2287.6].index.values.astype(int)

Но мне возвращается просто пустой список: [].

В чем может быть проблема? Также, как можно получить значение из другой колонки, которое находится на этой же строке?

Вы можете сначала преобразовать столбцы к нужному типу данных, а потом делать поиск:

df["Сумма"] = pd.to_numeric(df["Сумма"], errors="coerce")
idx = df[df['Сумма'] == 2287.6].index
print(idx.to_list())
# [5]

получить значение по найденному индексу из другого столбца – возвращается объект типа pandas.Series:

In [89]: print(df.loc[idx, "Начало"])
5    2020-04-02
Name: Начало, dtype: object

чтобы вернуть скалярное значение:

In [91]: print(df.at[idx[0], "Начало"])
# 2020-04-02

PS официальная документация об индексировании и доступе к данным в Pandas

ответ дан 22 дек 2021 в 20:59

How can I get the number of the row in a dataframe that contains a certain value in a certain column using Pandas? For example, I have the following dataframe:

     ClientID  LastName
0    34        Johnson
1    67        Smith
2    53        Brows  

How can I find the number of the row that has ‘Smith’ in ‘LastName’ column?

asked Apr 3, 2017 at 20:42

 len(df[df["Lastname"]=="Smith"].values)

answered Sep 5, 2018 at 13:13

You can simply use shape method
df[df['LastName'] == 'Smith'].shape

Output
(1,1)

Which indicates 1 row and 1 column. This way you can get the idea of whole datasets

Let me explain the above code
DataframeName[DataframeName['Column_name'] == 'Value to match in column']

answered Apr 30, 2020 at 1:46

I know it’s many years later but don’t try the above solutions without reindexing your dataframe first. As many have pointed out already the number you see to the left of the dataframe 0,1,2 in the initial question is the index INSIDE that dataframe. When you extract a subset of it with a condition you might end up with 0,2 or 2,1, or 2,1 or 2,1,0 depending your condition. So by using that number (called “index”) you will not get the position of the row in the subset. You will get the position of that row inside the main dataframe.

use:

np.where([df['LastName'] == 'Smith'])[1][0]

and play with the string ‘Smith’ to see the various outcomes. Where will return 2 arrays. The 2nd one (index 1) is the one you care about.

NOTE:
When the value you search for does not exist where() will return 0 on [1][0]. When is the first value of the list it will also return 0 on [1][0]. Make sure you validate the existence first.

NOTE #2:
In case the same value as in your condition is present in the subset multiple times on [1] with will find the list with the position of all occurrences. You can use the length of [1] for future processing if needed.

answered Jan 6, 2022 at 18:56

If in the question “row number” means actual row number/position (rather than index label)
pandas.Index.get_loc(key, method=None, tolerance=None)
seems to be the answer, ie something like:

row_number = df.index.get_loc(df.query(f'numbers == {m}').index[0])  

The current answers, except one, explain how to get the index label rather than the row number.
Trivial code with index lables not corresponding to row numbers:

import pandas as pd

n = 3; m = n-1

df = pd.DataFrame({'numbers' : range(n) },
    index = range(n-1,-1,-1))
print(df,"n")

label =      df[df['numbers'] == m].index[0]
row_number = df.index.get_loc(df.query(f'numbers == {m}').index[0])

print(f'index label: {label}nrow number:  {row_number}',"n")
print(f"df.loc[{label},'numbers']: {df.loc[label, 'numbers']}")
print(f"df.iloc[{row_number}, 0]:       {df.iloc[row_number, 0]}")

   numbers
2        0
1        1
0        2 

index label: 0
row number:  2 

df.loc[0,'numbers']: 2
df.iloc[2, 0]:       2

answered Aug 9, 2022 at 20:17

1. To get exact row-number of single occurrence

row-number = df[df["LastName" == 'Smith']].index[0]

1. To get exact row-number of multiple occurrence of ‘Smith’

row-number = df[df["LastName" == 'Smith']].index.tolist()

answered Nov 30, 2022 at 15:57