如何为每个拆分执行命令？

Question

I am new to python, and am trying to filter a string that looks similar to this:

"{Red,Plant,Eel}{Blue,Animal,Maple}{Yellow,Plant,Crab}"

And so on for 100s of three word sets.

I want to extract the second word from every set marked by "{ }", so in this example I want the output:

"Plant,Animal,Plant"

And so on.

How can I do it efficiently?

As of Right now I am using string.split(",")[1] individually for each "{ }" group.

Thanks.

Answer 1

This does the trick:

str_ = "{Red,Plant,Eel}{Blue,Animal,Maple}{Yellow,Plant,Crab}"
res = [x.split(',')[1] for x in str_[1:-1].split('}{')]

and produces

['Plant', 'Animal', 'Plant']

---

with the str_[1:-1] we remove the initial "{" and trailing "}" and we then split the remaining entities on every instance of "}{" thus producing:

["Red,Plant,Eel", "Blue,Animal,Maple", ...]

finally, for every string, we split on "," to obtain

[["Red", "Plant", "Eel"], ...]

from which we keep only the first element of each sublist with x[1] .

Note that for your specific purpose, slicing the original string with str_[1:-1] is not mandatory (works without it as well), but if you wanted only the first instead of the second item it would make a difference. The same holds in case you wanted the 3rd.

---

If you want to concatenate the strings of the output to match your desired result, you can simply pass the resulting list to .join as follows:

out = ','.join(res)

which then gives you

"Plant,Animal,Plant"

Answer 2

尝试这个：

[i.split(',')[1] for i in str_[1:].split('}')[:len(str_.split('}'))-1]]

Answer 3

another solution is using regex, a bit more complicated, but it's a technique worth talking about:

import re
input_string = "{Red,Plant,Eel}{Blue,Animal,Maple}{Yellow,Plant,Crab}"
regex_string = "\{\w+\,(\w+)\,\w+\}"

result_list = re.findall(regex, input_string)

then result_list output is:

['Plant', 'Animal', 'Plant']

here's a link for regex in python and an online regex editor

Answer 4

#!/bin/python3

string = "{Red,Plant,Eel}{Blue,Animal,Maple}{Yellow,Plant,Crab}"
a = string.replace('{','').replace('}',',').split(',')[1::3]
print(a)

result is ['Plant', 'Animal', 'Plant']