8.3: Searching/Testing Strings
- Page ID
- 117573
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- Use the
inoperator to identify whether a given string contains a substring. - Call the
count()method to count the number of substrings in a given string. - Search a string to find a substring using the
find()method. - Use the
index()method to find the index of the first occurrence of a substring in a given string. - Write a for loop on strings using in operator.
in operator
The in Boolean operator can be used to check if a string contains another string. in returns True if the first string exists in the second string, False otherwise.
1.
What is the output of ("a" in "an umbrella")?
-
2
FalseTrue12.
What is the output of ("ab" in "arbitrary")?
-
True -
False
3.
What is the output of ("" in "string")?
-
True -
False
For loop using in operator
The in operator can be used to iterate over characters in a string using a for loop. In each for loop iteration, one character is read and will be the loop variable for that iteration.
4.
What is the output of the following code?
for c in "string":
print(c, end = "")
-
string
s
t
r
i
n
g
s t r i n g
5.
What is the output of the following code?
count = 0
for c in "abca":
if c == "a":
count += 1
print(count)
-
0 -
1 -
2
6.
What is the output of the following code?
word = "cab"
for i in word:
if i == "a":
print("A", end = "")
if i == "b":
print("B", end = "")
if i == "c":
print("C", end = "")
-
cab -
abc -
CAB -
ABC
count()
The count() method counts the number of occurrences of a substring in a given string. If the given substring does not exist in the given string, the value 0 is returned.
7.
What is the output of (aaa".count("a"))?
-
True
138.
What is the output of ("weather".count("b"))?
-
0 -
-1 -
False
9.
What is the output of ("aaa".count("aa"))?
-
1 -
2 -
3
find()
The find() method returns the index of the first occurrence of a substring in a given string. If the substring does not exist in the given string, the value of -1 is returned.
10.
What is the output of"banana".find("a")?
-
1
3511.
What is the output of"banana".find("c")?
-
0 -
-1 -
ValueError
12.
What is the output of"b".find("banana")?
-
-1 -
0 -
ValueError
index()
The index() method performs similarly to the find() method in which the method returns the index of the first occurrence of a substring in a given string. The index() method assumes that the substring exists in the given string; otherwise, throws a ValueError.
Getting the time's minute portion
Consider a time value is given as part of a string using the format of "hh:mm" with "hh" representing the hour and "mm" representing the minutes. To retrieve only the string's minute portion, the following code can be used:
time_string = "The time is 12:50"
index = time_string.index(":")
print(time_string[index+1:index+3])
The above code's output is:
50
13.
What is the output of"school".index("o")?
-
3
4-314.
What is the output of"school".index("ooo")?
-
3 -
4 -
ValueError
15.
What is the output of the following code?
sentence = "This is a sentence"
index = sentence.index(" ")
print(sentence[:index])
-
"This" -
"This " -
"sentence"
Write a program that, given a string, counts the number of space characters in the string. Also, print the given string with all spaces removed.
Input: "This is great"
Prints:
2
Thisisgreat