Create a function to concatenate string in Python

I have a Pandas df as defined below:

    ID     Start          End
0   77     2018-07-02    2020-07-02
1   88     2019-07-02    2021-07-02
2   99     2020-07-02    2022-07-02

I want to create a function to return the following result (string):

((Date BETWEEN '2018-07-02' AND '2020-07-02') AND ID = 77)
OR ((Date BETWEEN '2019-07-02' AND '2021-07-02') AND ID = 88)
OR ((Date BETWEEN '2020-07-02' AND '2022-07-02') AND ID = 99)

Here is what I have written, but it did not generate the expected result:

def create_string(df):
    date_start = df.loc[
       (df['ID'] == ID), 'Start']
    date_end = df.loc[
       (df['ID'] == ID), 'End']
    date_string = F"(((Date BETWEEN '{date_start}' AND '{date_end}') AND ID = '{ID}') OR"
    string = ""
    final_string = string + date_string
    return final_string

IDs = df.ID.copy()

for ID in IDs:
    print(create_string(df))

Any suggestions would be greatly appreciated!

you can do like this

df["cond"] = df.apply(lambda r: f"((Date BETWEEN '{r['start']}' AND 'r['end']') AND ID = r['ID'])", axis=1)

then the out string can be calculated by

final_str = " OR ".join(df["cond"].tolist())

Got an example working:

import pandas as pd

d = {'ID': [77,78,99], 'Start': ['2018-07-02', '2018-07-03', '2018-07-04'], 
     'End': ['2018-07-05', '2018-07-06', '2018-07-07']}


df = pd.DataFrame(data=d)

def create_string(df, id_, string):
    date_start = df.loc[df['ID'] == id_].iloc[0,1]
    date_end = df.loc[df['ID'] == id_].iloc[0,2]
    date_string = F"(((Date BETWEEN '{date_start}' AND '{date_end}') AND ID = '{id_}') OR"
    string += date_string
    return string


string = ""
for id_ in [77, 78,99]:
    string = create_string(df,id_, string)
print(string)

Your problems were:

• some indexation mistakes in the dataframe selection.
• the string redefinition each time in the function
• the function not returning the new string value

You are almost there. You just need to call values[0] when accessing the dates and make minor changes to function paramters.

def create_string(df, ID):
    date_start = df.loc[
       (df['ID'] == ID), 'Start'].values[0]
    date_end = df.loc[
       (df['ID'] == ID), 'End'].values[0]
    date_string = f"((Date BETWEEN '{date_start}' AND '{date_end}') AND ID = {ID})"
    return date_string
    

IDs = df.ID.copy()
strings = []

for ID in IDs:
    strings.append(create_string(df, ID))

print(" OR\n".join(strings))

Alternatively, you could write it in this manner. This makes your code look much cleaner.

def get_dates(df, ID):
    date_start = df.loc[df['ID'] == ID, 'Start'].values[0]
    date_end = df.loc[df['ID'] == ID, 'End'].values[0]
    return date_start, date_end

def create_date_string(df, ID):
    date_start, date_end = get_dates(df, ID)
    date_string = f"((Date BETWEEN '{date_start}' AND '{date_end}') AND ID = {ID})"
    return date_string

def create_all_strings(df):
    IDs = df.ID.copy()
    all_strings = [create_date_string(df, ID) for ID in IDs]
    return " OR\n".join(all_strings)

print(create_all_strings(df))

Assuming some parenthesis are redundant, following will work with any data-frame with above shape.

' OR '.join(map(lambda r: "(DATE BETWEEN '{}' AND '{}' AND ID = {})".format(r[1], r[2], r[0]), df.values.tolist()))

Output:

"(DATE BETWEEN '2018-07-02' AND '2020-07-02' AND ID = 77) OR (DATE BETWEEN '2019-07-02' AND '2021-07-02' AND ID = 88) OR (DATE BETWEEN '2020-07-02' AND '2022-07-02' AND ID = 99)"