Don't understand output

小能豆

Don't understand output

python

I’m new to this site so please forgive any mistakes or misconceptions I may have. I’m new to Python and am currently working through a tutorial. I have come across the following input (apparently very simple) but I cannot understand the sequence in the answer.

Code is as follows

pattern = r"\W"  # Matches any non-word character
text = "Hello, world!"
matches = re.findall(pattern, text)

print("Matches:", matches)`

Output is

Matches: [',', ' ', '!']

The tutorial then gives this statement to aid understanding:

The regular expression pattern is defined as r”\W”, which uses the \W special sequence to match any character that is not a word character (a-z, A-Z, 0-9, or _). The string we’re searching for matches in is “Hello, world!”.

N.B. “import re” had been previously input.

My problem is that I don’t understand how the sequence of quotation marks and commas marry up with “Hello, world” - that is I don’t know what they all mean in the order they are given.

If anyone can offer any advance I would be very grateful.

Many thanks in advance.

I have read through the sequence and comments many times but still cannot understand the order of the sequence.

阅读 82

2023-12-07

共1个答案

小能豆

I’ll break down the code and the regular expression pattern for you:

import re

pattern = r"\W"  # Matches any non-word character
text = "Hello, world!"
matches = re.findall(pattern, text)

print("Matches:", matches)

import re: This line imports the regular expression (regex) module in Python.
pattern = r"\W": This line defines a regular expression pattern. In this case, \W is a special sequence that matches any non-word character. The r before the string denotes a raw string, which means backslashes are treated as literal characters and not as escape characters.
text = "Hello, world!": This line defines a string containing the text you want to search for matches.
matches = re.findall(pattern, text): This line uses the findall function from the re module to find all non-overlapping occurrences of the pattern in the given text. The result is a list of matches.
print("Matches:", matches): This line prints the matches found in the text.

Now, let’s break down the regular expression pattern \W:

\W: In a regular expression, \W is a special sequence that matches any non-word character. A word character, in this context, is defined as any alphanumeric character (a-z, A-Z, 0-9) or an underscore _. Therefore, \W matches anything that is not a word character.

In the given example, the text is “Hello, world!” and the non-word characters are ',', ' ', and '!'. The re.findall function finds all occurrences of these non-word characters in the text and returns them as a list.

So, the output “Matches: [‘,’, ‘ ‘, ‘!’]” indicates that these non-word characters were found in the input text “Hello, world!”.

2023-12-07