How to compare list using contains() for initial substrings with Python Pandas?

Question

I have some list values I want to check against another list of conditions.

For example, the condition list I want to check against is ['042', '043', '044']. I want to return True as long as the initial substring contains any of these values.

For example, ['04233'], ['042'] or ['042', '011'] should return True. But for ['11042'] or ['13044'], even though it contains the check conditions as substring, because they are not the initial characters, they should return False.

My code is as follows:

import pandas as pd

df = pd.DataFrame(['152042']) #'04211'
df.columns=['test_list']

cond_list = ['042', '043', '044']

print (df['test_list'].str.contains('|'.join(cond_list)).any())

# Return True, but False is desired.

I am not sure how I can incorporating both substring checking and at the same time ensuring the subtrings occur as leading characters.

Use ^ to assert a match at the start of a string

user3483203
– user3483203

2018-12-11 19:47:37 +00:00
Commented Dec 11, 2018 at 19:47 — user3483203
– user3483203, Commented Dec 11, 2018 at 19:47
change contains to startswith

BENY
– BENY

2018-12-11 19:49:39 +00:00
Commented Dec 11, 2018 at 19:49 — BENY
– BENY, Commented Dec 11, 2018 at 19:49
@user3483203 let me write it to an answer .

BENY
– BENY

2018-12-11 19:51:39 +00:00
Commented Dec 11, 2018 at 19:51 — BENY
– BENY, Commented Dec 11, 2018 at 19:51
xion.io/post/code/python-startswith-tuple.html

ely
– ely

2018-12-11 19:54:09 +00:00
Commented Dec 11, 2018 at 19:54 — ely
– ely, Commented Dec 11, 2018 at 19:54

BENY · Accepted Answer · 2018-12-11 19:52:07Z

3

Using startswith, notice it accpet tuple not list

df['test_list'].str.startswith(tuple(cond_list))
Out[47]: 
0    False
Name: test_list, dtype: bool

answered Dec 11, 2018 at 19:52

BENY

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Comments

user3483203 · Accepted Answer · 2018-12-11 20:00:36Z

2

You've got the general idea, you just need to add an assertion to match at the beginning of your string, using a ^ character.

rgx = '^({})'.format('|'.join(cond_list))
# '^(042|043|044)'

df['test_list'].str.contains(rgx).any()

False

edited Dec 11, 2018 at 20:00

answered Dec 11, 2018 at 19:53

user3483203

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2 Comments

KubiK888 Over a year ago

I got a warning "UserWarning: This pattern has match groups. To actually get the groups, use str.extract. 1 if row[var_name_list].str.contains(rgx).any() else 0, axis=1)", is this not a concern?

user3483203 Over a year ago

Not a concern, if the warning bothers you, you can convert the matching group to be non-capturing: rgx = '^(?:{})'.format('|'.join(cond_list))

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