Python PANDAS: Conditionally Insert Character in String Field

Question

What would be the best way to insert a character conditionally in a PANDAS string field with the following criteria:

Insert a "." after the first 3 numeric characters from the left (ignore letters)
Do not add a "." if there are no additional characters trailing
```
96501
E0000
V909
965
```
Becomes
```
965.01
E000.0
V909
965
```

akuiper · Accepted Answer · 2017-11-03 21:49:28Z

1

You can capture the first three digits with ((?:\D*\d){3}), use (?=.+) to assert there is at least one more character following, and use back reference to add . to the captured pattern:

df[0].str.replace(r'^((?:\D*\d){3})(?=.+)', r'\1.')
#0    965.01
#1    E000.0
#2      V909
#3       965
#Name: 0, dtype: object

answered Nov 3, 2017 at 21:49

akuiper

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2 Comments

Pylander Over a year ago

Thanks for the quick answer! If you would not mind, what would also be a version that would count alpha and numeric from the left?

akuiper Over a year ago

If both alpha and numeric, you can use ^((?:[^a-zA-Z0-9]*[a-zA-Z0-9]){3})(?=.+).

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