0

this is simple question but i don't know why i cannot compare if corectly.

df:

A,B
1,marta
2,adam1
3,kama
4,mike

i want to print 'exist' if specific name exist in df

for example, i want to check if marta exist in df['B']

code:

string='www\marta2'
if df['B'].str.contains(string,regex=False).all()==True:
    print('exist')
else:
    print('not exist')

when i am using .bool() instead of all() i am receiving error: ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

I am reveiving False on each line, why ? should i compare this type of string some how in different way?

EDIT: I need to use IF statement because in my code instead of print my code need to assigh variables, normaly i would use different way. If my string='marta' it works well but with additional string not

EDIT: 

new code:
string='www\marta2'
    if df['B'].str.rfind(string).any():
        print('exist')
    else:
        print('not exist')
but it compares everything, so even if one letter is in column it will print 'exist'
Improve this question
2
  • Your problem is that 'marta' does not contain 'www\marta2'. This: string='mart'; print(df['B'].str.contains(string,regex=False).any()) does print True... Commented Jun 12, 2019 at 10:14
  • You can see in my answer the loop will terminate if the value is found. You need not have to go through the elements further, if the condition is satisfied. Commented Jun 12, 2019 at 12:17

3 Answers 3

Reset to default
1

if you want to check if the string exists at all in the whole df, use any() instead of all().

If you want to check if the string exists for each row, you can create a new column and don't have to use if statement

df.loc[df['B'].str.contains(string,regex=False), 'C'] = 'exist'
df.loc[~(df['B'].str.contains(string,regex=False)), 'C'] = 'not exist'

EDIT: I tried this and it works as long as the string is exactly what you're looking for.

string='www\marta2'
if df['name'].str.contains(string,regex=False).any():
    print('exist')
else:
    print('not exist')
Improve this answer
Sign up to request clarification or add additional context in comments.

5 Comments

hey,. please see my edits, i need to use IF anyway, becasue id True my var=1 or 0 in my real code
Can you give me a few example of what your strings look like? It might be a problem to be solved with regex
my string looks same as in my example var string
is that the exact string you're looking for in the dataframe? Please see my EDIT
i need to check if this specific string exist in specific column, i dont need to choose rows
0

May be this will help you: 

>>> for b in df["B"].values:
...     if string.rfind(b) != -1:
...         print("exists")
...         break
...

The looping which is for loop includes df["B"].values which returns array values of column B. Now if you have the array you can loop through it and thus get the output.
In the condition if statement, I have just compared each of the values of the B column. rfind() given the output of the partially matched string output or substring.
It thus the magic.

Improve this answer

9 Comments

interesting way, could you explain it ? its working for me
@sygneto I have added the explanation to the answer. please check if you got it. Accept the answer if it helps you can also upvote answers here. It encourages who answers.
@sygneto Thank you for your upvote. If the answer is helpful then please accept it.
is there any option to avoid for loop?
@sygneto What is the issue with for loop? Ultimately you have to loop through the elements right?
|
0

answer on my question: to recive only one answer if string exist or not in column, good way is to use df.str.contains(), as we know str.contains is comparing only whole string, that's why my first code doesn't work. second way is to use rfind but it will be always true because this function is comparing single letters in my case.

the answer is to prepare string that i am comparing to receive expected result

string='www\marta2'
new_string=string.split('\\')[-1][0:5]
if df['B'].str.contains(new_string,regex=False).any():
    print('exist')
else:
    print('not exist')
Improve this answer

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.