Regular Expressions

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RegEx1.py

#!/usr/bin/env python3;
import Utils
import re

# Begin Main
s = "Four score and seven years ago..."
print("Match 1: " + str(Utils.defined(re.compile(r's.*e').search(s))))
print("Match 2: " + str(Utils.defined(re.compile(r'\bs.*e\b').search(s))))
print("Match 3: " + str(Utils.defined(re.compile(r's...e').search(s))))
print("Match 4: " + str(Utils.defined(re.compile(r'b.d').search(s))))

subgroups = Utils.findFirst(re.compile(r'(\w+)\s*(\w+)'), s)
print("Find First (with subgroups): " + Utils.listToString(subgroups))
subgroups = Utils.findFirst(re.compile(r'bad match'), s)
print("Find First (bad match): " + Utils.listToString(subgroups))

matches = re.compile(r'\w+').findall(s)
print("Find All: (matches only)" + Utils.listToString(matches))
matches = re.compile(r'bad match').findall(s)
print("Find All (bad match): " + Utils.listToString(matches))

Output

$ python3 RegEx1.py Match 1: True Match 2: True Match 3: True Match 4: False Find First (with subgroups): ["Four score", "Four", "score"] Find First (bad match): [] Find All: (matches only)["Four", "score", "and", "seven", "years", "ago"] Find All (bad match): []

RegEx2.py

#!/usr/bin/env python3;
import Utils
import re

# Begin Main
s = "Four score and seven years ago..."
print("Replace First 1: " + re.compile(r'\.\.\.').sub("!!!", s, 1))
print("Replace First 2: " + re.compile(r'\b...\b').sub("???", s, 1))
print("Replace First 3: " + re.compile(r'b.d').sub("???", s, 1))
print("Replace First 4: " + re.compile(r'(\w+) (\w+)').sub(re.compile(r'\2 \1'), s, 1))

print("Replace All 1: " + re.compile(r'\b...\b').sub("???", s))
print("Replace All 2: " + re.compile(r'(\w+) (\w+)').sub(re.compile(r'\2 \1'), s))

Output

$ python3 RegEx2.py Replace First 1: Four score and seven years ago!!! Replace First 2: Four score ??? seven years ago... Replace First 3: Four score and seven years ago... Traceback (most recent call last): File "/Users/rich/Desktop/Resources/pureprogrammer/py/examples/RegEx2.py", line 10, in <module> print("Replace First 4: " + re.compile(r'(\w+) (\w+)').sub(re.compile(r'\2 \1'), s, 1)) File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/re.py", line 252, in compile return _compile(pattern, flags) File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/re.py", line 304, in _compile p = sre_compile.compile(pattern, flags) File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/sre_compile.py", line 764, in compile p = sre_parse.parse(p, flags) File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/sre_parse.py", line 948, in parse p = _parse_sub(source, state, flags & SRE_FLAG_VERBOSE, 0) File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/sre_parse.py", line 443, in _parse_sub itemsappend(_parse(source, state, verbose, nested + 1, File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/sre_parse.py", line 525, in _parse code = _escape(source, this, state) File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/sre_parse.py", line 423, in _escape raise source.error("invalid group reference %d" % group, len(escape) - 1) re.error: invalid group reference 2 at position 1

RegEx3.py

#!/usr/bin/env python3;
import Utils
import re

# Begin Main
str = "Four score and seven years ago..."
print("Split 1: " + Utils.listToString(re.compile(r' ').split(str)))
print("Split 2: " + Utils.listToString(re.compile(r'[eo]').split(str)))
print("Split 3: " + Utils.listToString(re.compile(r'\s').split(str)))
print("Split 4: " + Utils.listToString(re.compile(r'\W').split(str)))

Output

$ python3 RegEx3.py Split 1: ["Four", "score", "and", "seven", "years", "ago..."] Split 2: ["F", "ur sc", "r", " and s", "v", "n y", "ars ag", "..."] Split 3: ["Four", "score", "and", "seven", "years", "ago..."] Split 4: ["Four", "score", "and", "seven", "years", "ago", "", "", ""]

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References

[[Python Language Reference]]
[[Python Standard Library]]
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