How to replace every second space with a comma the Pythonic way - python

I have a string with first and last names all separated with a space.
For example:
installers = "Joe Bloggs John Murphy Peter Smith"
I now need to replace every second space with ', ' (comma followed by a space) and output this as string.
The desired output is
print installers
Joe Bloggs, John Murphy, Peter Smith


You should be a able to do this with a regex that that finds the spaces and replaces the last one:
import re
installers = "Joe Bloggs John Murphy Peter Smith"
re.sub(r'(\s\S*?)\s', r'\1, ',installers)
# 'Joe Bloggs, John Murphy, Peter Smith'
This says, find a space followed by some non-spaces followed by a space and replace it with the found space followed by some non-spaces and ", ". You could add installers.strip() if there's a possibility of trailing spaces on the string.


One way to do this is to split the string into a space-separated list of names, get an iterator for the list, then loop over the iterator in a for loop, collecting the first name and then advancing to loop iterator to get the second name too.
names = installers.split()
it = iter(names)
out = []
for name in it:
next_name = next(it)
full_name = '{} {}'.format(name, next_name)
out.append(full_name)
fixed = ', '.join(out)
print fixed
'Joe Bloggs, John Murphy, Peter Smith'
The one line version of this would be
>>> ', '.join(' '.join(s) for s in zip(*[iter(installers.split())]*2))
'Joe Bloggs, John Murphy, Peter Smith'
this works by creating a list that contains the same iterator twice, so the zip function returns both parts of the name. See also the grouper recipe from the itertools recipes.

Related

New to Python: How to keep the first letter of each word capitalized?

I was practicing with this tiny program with the hopes to capitalize the first letter of each word in: john Smith.
I wanted to capitalize the j in john so I would have an end result of John Smith and this is the code I used:
name = "john Smith"
if (name[0].islower()):
name = name.capitalize()
print(name)
Though, capitalizing the first letter caused an output of: John smith where the S was converted to a lowercase. How can I capitalize the letter j without messing with the rest of the name?
I thank you all for your time and future responses!
I appreciate it very much!!!

As #j1-lee pointed out, what you are looking for is the title method, which will capitalize each word (as opposed to capitalize, which will capitalize only the first word, as if it was a sentence).
So your code becomes
name = "john smith"
name = name.title()
print(name) #> John Smith

Of course you should be using str.title(). However, if you want to reinvent that functionality then you could do this:
name = 'john paul smith'
r = ' '.join(w[0].upper()+w[1:].lower() for w in name.split())
print(r)
Output:
John Paul Smith
Note:
This is not strictly equivalent to str.title() as it assumes all whitespace in the original string is replaced with a single space

Detecting couples in photo captions with Python Regular Expressions

I'm working on a web scraping project where I am trying to extract names from a series of photo captions. I have the captions stored as a list of unicode strings such as:
Phil Collins, with Beth and Jerry Smith
I have been able to usefoo = re.compile(r" +with +|, +and +| +and +|, +") and re.split(foo) to separate the captions into different individual names such as:
['Phil Collins', 'Beth', 'Jerry Smith']
Unfortunately, I'm having trouble finding a way to split Jane and Jerry Smith (I'm new to regular expressions) in a way that can detect their surname and produce the output:
['Phil Collins', 'Beth Smith', 'Jerry Smith']
I am able to detect Beth and Jerry Smith using re.compile(r"[A-Z][a-z]+ +and +[A-Z][a-z]+ +[A-Z][a-z]+", but I am not sure the best way to process it once it is detected.
The problem I am trying to tackle is that I need to iterate over the list of names, detect that 'Beth' is not a full name, read 'Jerry Smith', and finally read and append 'Smith' to 'Beth' giving me a complete list of: ['Phil Collins', 'Beth Smith', 'Jerry Smith']
Is there a method in re that can pipe the matching substring to a function so I can modify it to include Beth's surname? Or am I even approaching this problem the right way?

Instead of searching the names and the delimiters with a complex RegEx, you could split the text using re.split and a smaller RegEx of all possible delimiters.
Here, the delimiters I see are: ", with" and "and" (with spaces at begin and end). You could create a RegEx by joining every delimiter.
import re
text = "Phil Collins, with Beth and Jerry Smith"
delimiters = [r",\s+with\s+", "\s+and\s+"]
regex = "|".join(delimiters)
print(re.split(regex, text, flags=re.IGNORECASE))
# -> ['Phil Collins', 'Beth', 'Jerry Smith']
EDIT
To join the "Beth" with "Smith" and "Jerry" with "Smith", you need to first split on the "with", and then split on the and.
import re
text = "Phil Collins, with Beth and Jerry Smith"
for part in re.split(",\s+with\s+", text):
first, last = re.findall(r"(\w+(?:\s+and\s+\w+)?)\s+(\w+)",
part, flags=re.UNICODE)[0]
names = re.split(r"\s+and\s+", first)
result = [name + " " + last
for name in names]
print(result)
You get:
['Phil Collins']
['Beth Smith', 'Jerry Smith']

Regex in Python: How to match a word pattern, if not preceded by another word of variable length?

I would like reconstruct full names from photo captions using Regex in Python, by appending last name back to the first name in patterns "FirstName1 and FirstName2 LastName". We can rely on names starting with capital letter.
For example,
'John and Albert McDonald' becomes 'John McDonald' and 'Albert McDonald'
'Stephen Stewart, John and Albert Diamond' becomes 'John Diamond' and 'Albert Diamond'
I would need to avoid matching patterns like this: 'Jay Smith and Albert Diamond' and generate a non-existent name 'Smith Diamond'
The photo captions may or may not have more words before this pattern, for example, 'It was a great day hanging out with John and Stephen Diamond.'
This is the code I have so far:
s = 'John and Albert McDonald'
so = re.search('([A-Z][a-z\-]+)\sand\s([A-Z][a-z\-]+\s[A-Z][a-z\-]+(?:[A-Z][a-z]+)?)', s)
if so:
print so.group(1) + ' ' + so.group(2).split()[1]
print so.group(2)
This returns 'John McDonald' and 'Albert McDonald', but 'Jay Smith and Albert Diamond' will result in a non-existent name 'Smith Diamond'.
An idea would be to check whether the pattern is preceded by a capitalized word, something like (?<![A-Z][a-z\-]+)\s([A-Z][a-z\-]+)\sand\s([A-Z][a-z\-]+\s[A-Z][a-z\-]+(?:[A-Z][a-z]+)?) but unfortunately negative lookbehind only works if we know the exact length of the preceding word, which I don't.
Could you please let me know how I can correct my regex epression? Or is there a better way to do what I want? Thanks!

As you can rely on names starting with a capital letter, then you could do something like:
((?:[A-Z]\w+\s+)+)and\s+((?:[A-Z]\w+(?:\s+|\b))+)
Live preview
Swapping out your current pattern, with this pattern should work with your current Python code. You do need to strip() the captured results though.
Which for your examples and current code would yield:
Input
First print
Second print
John and Albert McDonald
John McDonald
Albert McDonald
Stephen Stewart, John and Albert Diamond
John Diamond
Albert Diamond
It was a great day hanging out with John and Stephen Diamond.
John Diamond
Stephen Diamond

pywikipedia (python) regex to add string if lacking

I have a set of records like:
Name
Name Paul Berry: present
Address George Necky: not present
Name Bob van Basten: present
Name Richard Von Rumpy: not present
Name Daddy Badge: not present
Name Paul Berry: present
Street George Necky: not present
Street Bob van Basten: present
Name Richard Von Rumpy: not present
City Daddy Badge: not present
and I want that all the records beginning with Name be in the form
Name Name Surname: not present
leaving untouched the records beginnning with other word.
i.e. I want to add the string "not" to the records beginning with Name where it isn't. I'm working with python (pywikipediabot)
Trying
python replace.py -dotall -regex 'Name ((?!not ).*?)present' 'Name \1not present'
but it adds the "not" even where it is already present.
Perhaps I haven't understood the negative lookahead syntax?

Just look for : present and replace it with : not present.
Edit: Improved answer:
for line in lines:
m = re.match('^Name[^:]*: present', line)
if m:
print re.sub(': present', ': not present', line)
else:
print line

You need a "negative look-behind" expression. This substitution will work:
'Name (.*)(?<!not )present' -> 'Name \1not present'
The .* matches everything between "Name" and "present", but the whole regexp matches only if "present" is not preceded by "not".
And are you sure you need -dotall? It looks like you want .* to match within a line only.

The following will do it:
re.sub(r'(Name.*?)(not )?present$', r'\1not present', s)

How to split a string by commas positioned outside of parenthesis?

I got a string of such format:
"Wilbur Smith (Billy, son of John), Eddie Murphy (John), Elvis Presley, Jane Doe (Jane Doe)"
so basicly it's list of actor's names (optionally followed by their role in parenthesis). The role itself can contain comma (actor's name can not, I strongly hope so).
My goal is to split this string into a list of pairs - (actor name, actor role).
One obvious solution would be to go through each character, check for occurances of '(', ')' and ',' and split it whenever a comma outside occures. But this seems a bit heavy...
I was thinking about spliting it using a regexp: first split the string by parenthesis:
import re
x = "Wilbur Smith (Billy, son of John), Eddie Murphy (John), Elvis Presley, Jane Doe (Jane Doe)"
s = re.split(r'[()]', x)
# ['Wilbur Smith ', 'Billy, son of John', ', Eddie Murphy ', 'John', ', Elvis Presley, Jane Doe ', 'Jane Doe', '']
The odd elements here are actor names, even are the roles. Then I could split the names by commas and somehow extract the name-role pairs. But this seems even worse then my 1st approach.
Are there any easier / nicer ways to do this, either with a single regexp or a nice piece of code?

One way to do it is to use findall with a regex that greedily matches things that can go between separators. eg:
>>> s = "Wilbur Smith (Billy, son of John), Eddie Murphy (John), Elvis Presley, Jane Doe (Jane Doe)"
>>> r = re.compile(r'(?:[^,(]|\([^)]*\))+')
>>> r.findall(s)
['Wilbur Smith (Billy, son of John)', ' Eddie Murphy (John)', ' Elvis Presley', ' Jane Doe (Jane Doe)']
The regex above matches one or more:
non-comma, non-open-paren characters
strings that start with an open paren, contain 0 or more non-close-parens, and then a close paren
One quirk about this approach is that adjacent separators are treated as a single separator. That is, you won't see an empty string. That may be a bug or a feature depending on your use-case.
Also note that regexes are not suitable for cases where nesting is a possibility. So for example, this would split incorrectly:
"Wilbur Smith (son of John (Johnny, son of James), aka Billy), Eddie Murphy (John)"
If you need to deal with nesting your best bet would be to partition the string into parens, commas, and everthing else (essentially tokenizing it -- this part could still be done with regexes) and then walk through those tokens reassembling the fields, keeping track of your nesting level as you go (this keeping track of the nesting level is what regexes are incapable of doing on their own).

s = re.split(r',\s*(?=[^)]*(?:\(|$))', x)
The lookahead matches everything up to the next open-parenthesis or to the end of the string, iff there's no close-parenthesis in between. That ensures that the comma is not inside a set of parentheses.

I think the best way to approach this would be to use python's built-in csv module.
Because the csv module only allows a one character quotechar, you would need to do a replace on your inputs to convert () to something like | or ". Then make sure you are using an appropriate dialect and off you go.

An attempt on human-readable regex:
import re
regex = re.compile(r"""
# name starts and ends on word boundary
# no '(' or commas in the name
(?P<name>\b[^(,]+\b)
\s*
# everything inside parentheses is a role
(?:\(
(?P<role>[^)]+)
\))? # role is optional
""", re.VERBOSE)
s = ("Wilbur Smith (Billy, son of John), Eddie Murphy (John), Elvis Presley,"
"Jane Doe (Jane Doe)")
print re.findall(regex, s)
Output:
[('Wilbur Smith', 'Billy, son of John'), ('Eddie Murphy', 'John'),
('Elvis Presley', ''), ('Jane Doe', 'Jane Doe')]

My answer will not use regex.
I think simple character scanner with state "in_actor_name" should work. Remember then state "in_actor_name" is terminated either by ')' or by comma in this state.
My try:
s = 'Wilbur Smith (Billy, son of John), Eddie Murphy (John), Elvis Presley, Jane Doe (Jane Doe)'
in_actor_name = 1
role = ''
name = ''
for c in s:
if c == ')' or (c == ',' and in_actor_name):
in_actor_name = 1
name = name.strip()
if name:
print "%s: %s" % (name, role)
name = ''
role = ''
elif c == '(':
in_actor_name = 0
else:
if in_actor_name:
name += c
else:
role += c
if name:
print "%s: %s" % (name, role)
Output:
Wilbur Smith: Billy, son of John
Eddie Murphy: John
Elvis Presley:
Jane Doe: Jane Doe

Here's a general technique I've used in the past for such cases:
Use the sub function of the re module with a function as replacement argument. The function keeps track of opening and closing parens, brackets and braces, as well as single and double quotes, and performs a replacement only outside of such bracketed and quoted substrings. You can then replace the non-bracketed/quoted commas with another character which you're sure doesn't appear in the string (I use the ASCII/Unicode group-separator: chr(29) code), then do a simple string.split on that character. Here's the code:
import re
def srchrepl(srch, repl, string):
"""Replace non-bracketed/quoted occurrences of srch with repl in string"""
resrchrepl = re.compile(r"""(?P<lbrkt>[([{])|(?P<quote>['"])|(?P<sep>["""
+ srch + """])|(?P<rbrkt>[)\]}])""")
return resrchrepl.sub(_subfact(repl), string)
def _subfact(repl):
"""Replacement function factory for regex sub method in srchrepl."""
level = 0
qtflags = 0
def subf(mo):
nonlocal level, qtflags
sepfound = mo.group('sep')
if sepfound:
if level == 0 and qtflags == 0:
return repl
else:
return mo.group(0)
elif mo.group('lbrkt'):
level += 1
return mo.group(0)
elif mo.group('quote') == "'":
qtflags ^= 1 # toggle bit 1
return "'"
elif mo.group('quote') == '"':
qtflags ^= 2 # toggle bit 2
return '"'
elif mo.group('rbrkt'):
level -= 1
return mo.group(0)
return subf
If you don't have nonlocal in your version of Python, just change it to global and define level and qtflags at the module level.
Here's how it's used:
>>> GRPSEP = chr(29)
>>> string = "Wilbur Smith (Billy, son of John), Eddie Murphy (John), Elvis Presley, Jane Doe (Jane Doe)"
>>> lst = srchrepl(',', GRPSEP, string).split(GRPSEP)
>>> lst
['Wilbur Smith (Billy, son of John)', ' Eddie Murphy (John)', ' Elvis Presley', ' Jane Doe (Jane Doe)']

This post helped me a lot. I was looking to split a string by commas positioned outside quotes. I used this as a starter. My final line of code was regEx = re.compile(r'(?:[^,"]|"[^"]*")+') This did the trick. Thanks a ton.

I certainly agree with #Wogan above, that using the CSV moudle is a good approach. Having said that if you still want to try a regex solution give this a try, but you will have to adapt it to Python dialect
string.split(/,(?=(?:[^\"]*\"[^\"]*\")*(?![^\"]*\"))/)
HTH

split by ")"
>>> s="Wilbur Smith (Billy, son of John), Eddie Murphy (John), Elvis Presley, Jane Doe (Jane Doe)"
>>> s.split(")")
['Wilbur Smith (Billy, son of John', ', Eddie Murphy (John', ', Elvis Presley, Jane Doe (Jane Doe', '']
>>> for i in s.split(")"):
... print i.split("(")
...
['Wilbur Smith ', 'Billy, son of John']
[', Eddie Murphy ', 'John']
[', Elvis Presley, Jane Doe ', 'Jane Doe']
['']
you can do further checking to get those names that doesn't come with ().

None of the answers above are correct if there are any errors or noise in your data.
It's easy to come up with a good solution if you know the data is right every time. But what happens if there are formatting errors? What do you want to have happen?
Suppose there are nesting parentheses? Suppose there are unmatched parentheses? Suppose the string ends with or begins with a comma, or has two in a row?
All of the above solutions will produce more or less garbage and not report it to you.
Were it up to me, I'd start with a pretty strict restriction on what "correct" data was - no nesting parentheses, no unmatched parentheses, and no empty segments before, between or after comments - validate as I went, and then raise an exception if I wasn't able to validate.

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