在Python 3.x中查找功能

Question

When we have the following:

tweet2 = 'Want cheap snacks? Visit @cssu office in BA2283'

print(tweet2[tweet2.find('cheap')]) results in the output 'c' and I cant wrap my head around how it does this. I tried the visualizer and it didn't show anything. Could anyone please explain?

Answer 1

tweet2.find('cheap')返回找到“ cheap”开头的索引，并且在tweet2[index]使用该tweet2[index] ，它返回该索引处的字符，即“ c”

Answer 2

It's because the find(str, string) method determines if str occurs in string, or in a substring of string and returns the position of first occurrence. So when you call tweet2.find('cheap') it will return the position that is the first occurs of cheap.

Answer 3

You should consider reading python documentation on string methods and lists

# define string variable tweet2
tweet2 = 'Want cheap snacks? Visit @cssu office in BA2283'
# find position of substring 'cheap', which is 5 (strings has 0-based indices in python
n = tweet2.find('cheap')
# print 5th element of string, which is 'c'
print(tweet2[n])

Answer 4

find returns an index, not a slice.

If you want the full string you can get it like so:

to_find = 'cheap'
ind = tweet2.find(to_find)
print(tweet2[ind:ind+len(to_find)])