Python elif 无法按预期进行字符串查找

Question

I would like to pull out the locations for an inconsistently formatted data field in a Pandas dataframe. (I do not maintain the data so I cannot alter how this field is formatted.)

Running the following toy version

string2 = 'Denver.John'
if string2.find(' -'):
    string2 = string2.split(' -')[0]
elif string2.find('.'):
    string2 = string2.split('.')[0]
print(string2)

gives me Denver.John instead of Denver. However, if I use an if instead:

string2 = 'Denver.John'
if string2.find(' -'):
    string2 = string2.split(' -')[0]
if string2.find('.'):
    string2 = string2.split('.')[0]
print(string2)

I get Denver, as desired. The problem is I also have strings like 'Las.Vegas - Rudy' and I want to be able to pull out Las.Vegas in those instances so I only want to split on a period if the field does not contain the hyphen (' - ').

Why does the elif not work for Denver.John?

Answer 1

Because find either yields the index or -1 while -1 is valid,:!, so try using:

string2 = 'Denver.John'
if string2.find(' -') + 1:
    string2 = string2.split(' -')[0]
elif string2.find('.') + 1:
    string2 = string2.split('.')[0]
print(string2)

Or better like:

string2 = 'Denver.John'
if ' -' in string2:
    string2 = string2.split(' -')[0]
elif '.' in string2:
    string2 = string2.split('.')[0]
print(string2)

Answer 2

Use

if ' -' in string2

instead. The find method returns an int

Answer 3

find() returns the lowest index of the substring if it is found in given string. If it's not found then it returns -1.

So in your case:

string2 = 'Denver.John'
print(string2.find(' -')) # prints -1
print(string2.find('.')) # prints 6
if string2.find(' -'):
    string2 = string2.split(' -')[0]
elif string2.find('.'):
    string2 = string2.split('.')[0]
print(string2)

So in your if statement you can compare the result of find with -1 .

Answer 4

string.find returns a position of the substring, and it is -1 if it doesn't find the substring.

Thus, do the following instead:

string2 = 'Denver.John'
if string2.find(' -') >= 0:
    string2 = string2.split(' -')[0]
elif string2.find('.') >= 0:
    string2 = string2.split('.')[0]
print(string2)