How would I find the first occurrence of either the character e or o?
I want to do something like this:
my_string = "Hello World"
x = my_string.find('e' or 'o',my_string)
print x # 1
3 Answers
Use enumerate function with a generator expression, like this
>>> next(idx for idx, char in enumerate("Hello World") if char in 'eo')
1
It will give the index of the first character which is either e or o.
Note: It will fail if the characters are not there in the string. So, you can optionally pass the default value, like this
>>> next((idx for idx, char in enumerate("Hello World") if char in 'eo'), None)
1
>>> next((idx for idx, char in enumerate("Hi") if char in 'eo'), None)
None
2 Comments
Avinash Raj
What's the use of
next ?
thefourtheye
@AvinashRaj The argument passed to
enumerate is called a generator expression. It is like a normal function, but it can return values whenever you ask for the next value from it, till it exhausts.Alternatively, you could do a find on each character and then take the minimum of all the results (throwing away the -1s unless all of them are -1):
def first_index(string, search_chars):
finds = [string.find(c) for c in search_chars]
finds = [x for x in finds if x >= 0]
if finds:
return min(finds)
else:
return -1
This yields:
>>> first_index("Hello World", "eo")
1
>>> first_index("Hello World", "xyz")
-1
Comments
you can use collections.defaultdict:
>>> import collections
>>> my_dict = collections.defaultdict(list)
>>> for i,x in enumerate("hello world"):
... if x in "eo":
... my_dict[x].append(i)
...
>>> my_dict
defaultdict(<type 'list'>, {'e': [1], 'o': [4, 7]})
>>> my_dict['e'][0] # 1st 'e'
1
>>> my_dict['o'][0] # 1st 'o'
4
eoro?"