How to concatenate string to specific format using Python?

Question

Good morning,

I am a new python user and I am trying to replicate the following excel function in python:

=concatenate(left(H2,search(" ",H2,1)-1),if(LEN(right(H2,LEN(H2)-search(" ",H2,1)))=2,"00",if(LEN(right(H2,LEN(H2)-search(" ",H2,1)))=3,"0","")),right(H2,LEN(H2)-search(" ",H2,1)),"-KG")

I am trying to convert Highways into a format my computer program(arcgis) reads, basically turn my csv column format from:

the right column into the left column, so basically keep the two letter in the front (ex. US,FM,SL, CR) adding zeros in front making it a 4 digit highway always and adding "-KG" to the end.

thanks

Are you using pandas? Please show some sample data, and what code you've tried so far so that we can help you. — Chris
– Chris, Commented Oct 11, 2022 at 13:49

Steven Rumbalski · Accepted Answer · 2022-10-11 14:02:49Z

1

If using Python lists such as

arr = ['US 90', 'FM 1436', 'SL 305', 'US 277', 'FM 1589', 'SL 480']

do

result = [f'{s}{n:0>4}-KG' for s, n in map(str.split, arr)]

which gives

['US0090-KG', 'FM1436-KG', 'SL0305-KG', 'US0277-KG', 'FM1589-KG', 'SL0480-KG']

answered Oct 11, 2022 at 14:02

Steven Rumbalski

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JNevill · Accepted Answer · 2022-10-11 14:03:17Z

1

This would look something like:

import csv

with open("yourfile.csv") as fp:
    reader = csv.reader(fp, delimiter=" ")
    output = [[' '.join(row),f'{row[0]}{row[1].zfill(4)}-KG'] for row in reader]

print(output)

[['US 50', 'US0050-KG'], ['CA 987', 'CA0987-KG'], ['IL 4', 'IL0004-KG']]

The zfill() function will left pad a string with the 0 character to make the string the length of the argument (4 in this case)

If you are wanting to write that list of lists back out, check out this answer

answered Oct 11, 2022 at 14:03

JNevill

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2 Comments

Steven Rumbalski Over a year ago

{row[1].zfill(4)} in an fstring is more succinctly written {row[1]:0>4} but perhaps .zfill() is clearer.

JNevill Over a year ago

Totally agree. As usual there are a bunch of ways to skin this cat. I already dumped list comprehension in here so tossing in {row[1]:0>4} syntax isn't pushing it too far IMO.

Timo · Accepted Answer · 2022-10-11 21:09:29Z

This function converts the old highway format into your desired format:

def convert(highway):
    split = highway.split()
    prefix = split[0]
    number = split[1]
    return prefix + (4 - len(number))*"0" + number + "-KG"

If you're working with a pandas dataframe, this converts your whole column:

import pandas as pd

highways = ["US 90", "FM 1436", "SL 305", "US 277", "FM 1689", "SL 480"]

df = pd.DataFrame(highways, columns=["Highways"])
df["Highways"] = df["Highways"].transform(convert, axis=0)

print(df)

Out:

    Highways
0  US0090-KG
1  FM1436-KG
2  SL0305-KG
3  US0277-KG
4  FM1689-KG
5  SL0480-KG

Or if you're using a list:

highways = ["US 90", "FM 1436", "SL 305", "US 277", "FM 1689", "SL 480"]
new_highways = [convert(highway) for highway in highways]
print(new_highways)

Out:

['US0090-KG', 'FM1436-KG', 'SL0305-KG', 'US0277-KG', 'FM1689-KG', 'SL0480-KG']

SSD93 · Accepted Answer · 2022-10-11 14:27:43Z

0

You can try using the string format instead of zfill: Here's an example it's not for csv but in arcgis I think you wanted to use it in the atributte calculator.

List= ['US 90','FM 1436','SL 305']

for elem in List:
    Splited = str(elem).split(' ')
    Concatenated_elem = str(Splited[0]) + f'{int(Splited[1]):04d}' +'-KG'
    print(Concatenated_elem)

The result in this case is a print:

US0090-KG
FM1436-KG
SL0305-KG

Hope it helps,

edited Oct 11, 2022 at 14:27

answered Oct 11, 2022 at 14:19

SSD93

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4 Comments

Steven Rumbalski Over a year ago

{int(Splited[1]):04d} can be done without conversion to integer {Splited[1]:0>4} where 0 is the pad character, > means justify right, and 4 specifies the width.

SSD93 Over a year ago

Apparently you can not: Concatenated_elem = str(Splited[0]) + f'{Splited[1]:04d}' ValueError: Unknown format code 'd' for object of type 'str'

Steven Rumbalski Over a year ago

You used 04d, but should have used 0>4

bixb0012 Over a year ago

The Concatenated_elem is unnecessarily complicated, the reformatting can be done with a single f-string: f"{Splited[0]}{Splited[1]:0>4}-KG"

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