Author: John Au-Yeung

Sometimes, we want to extract part of a regex match with Python.

In this article, we’ll look at how to extract part of a regex match with Python.

How to extract part of a regex match with Python?

To extract part of a regex match with Python, we can use the re.search method with a regex that gets a match from within a pattern.

For instance, we write:

import re

html = '<title>hell world</title>'
title_search = re.search('<title>(.*)</title>', html, re.IGNORECASE)

if title_search:
    title = title_search.group(1)
print(title)

We want to extract the text between the title tags in html.

To do that, we call re.search with '<title>(.*)</title> to get the content between the title tags.

Then we pass in html and re.IGNORECASE as the other arguments to search html in a case-insensitive manner.

Then we get the match from the regex group with title_search.group(1).

Therefore, title should be 'hello world'.

Conclusion

To extract part of a regex match with Python, we can use the re.search method with a regex that gets a match from within a pattern.

Sometimes, we want to merge multiple data frames with Python Pandas.

In this article, we’ll look at how to merge multiple data frames with Python Pandas.

How to merge multiple data frames with Python Pandas?

To merge multiple data frames with Python Pandas, we can use the concat method.

For instance, we write:

import pandas as pd

data1 = {'a': [1, 2, 3]}
data2 = {'a': [4, 5, 6]}
df1 = pd.DataFrame(data1)
df2 = pd.DataFrame(data2)

merged_df = pd.concat([df1, df2])
print(merged_df)

We create 2 data frames with pd.DataFrame and 2 dictionaries.

Then we call pd.concat with the data frames in the list and assign the returned data frame to merged_df.

Therefore, merged_df is:

   a
0  1
1  2
2  3
0  4
1  5
2  6

Conclusion

To merge multiple data frames with Python Pandas, we can use the concat method.

Sometimes, we want to find all the factors of a number in Python.

In this article, we’ll look at how to find all the factors of a number in Python.

How to find all the factors of a number in Python?

To find all the factors of a number in Python, we can use the functools module.

For instance, we write:

from functools import reduce


def factors(n):
    return set(
        reduce(list.__add__, ([i, n // i]
                              for i in range(1,
                                             int(n**0.5) + 1) if n % i == 0)))


print(factors(50))

We define the factors function which takes the number n to get the factors from.

In the function, we call reduce with list.__add__ as the function to call to to add the factors into a list.

Then we compute the factors with ([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0) to compute the factors by getting all the numbers i that can divide n evenly.

Finally, we call set to remove the duplicates from the list returned by reduce.

Therefore, we should see {1, 2, 5, 10, 50, 25} from the print output.

Conclusion

To find all the factors of a number in Python, we can use the functools module.

Sometimes, we want to get the index of the returned max or min item using max()/min() on a list with Python.

In this article, we’ll look at how to get the index of the returned max or min item using max()/min() on a list with Python.

How to get the index of the returned max or min item using max()/min() on a list with Python?

To get the index of the returned max or min item using max()/min() on a list with Python, we can use the values.__getitem__ method as the value of the key parameter of min.

For instance, we write:

values = [1, 2, 3, 4, 5]
index_min = min(range(len(values)), key=values.__getitem__)
print(index_min)

We call min with range(len(values)) to get the min index of the item with the lowest value in the values list.

And we set key to values.__getitem__ to get the value from the index in the range(len(values)) generator so we can use the values in the values list for comparison.

Therefore, index_min is 0.

Conclusion

To get the index of the returned max or min item using max()/min() on a list with Python, we can use the values.__getitem__ method as the value of the key parameter of min.

Sometimes, we want to get the home directory in Python in a cross-platform way.

In this article, we’ll look at how to get the home directory in Python in a cross-platform way.

What is the correct cross-platform way to get the home directory in Python?

To get the home directory in Python in a cross-platform way, we can use the pathlib module.

For instance, we write:

from pathlib import Path

home = str(Path.home())
print(home)

to call Path.home to return the home directory value as an object.

Then we can convert it to a string with str and return it.

Therefore, home is something like '/home/runner'.

Conclusion

To get the home directory in Python in a cross-platform way, we can use the pathlib module.