جستجوی رشته در پایتون با تابع find و جایگزین کردن با replace در پایتون

phrase = "Hi my name is alireza"
phrase.find("Hi")
0
phrase.find("hi")
-1
phrase.find("my")
3
"Hi my name is alireza".find("my")
3
"I put a string in your string".find("string")
8
"my phone number is 5555-555-55".find("5")
19
"my phone number is 5555-555-55".find(str(5))
19
"my phone number is 5555-555-55".find(str(5-3))
-1

str1 = "my name is alireza, and alireza is my last name"
str1.replace("last","first")
'my name is alireza, and alireza is my first name'
str1
'my name is alireza, and alireza is my last name'
str1 = str1.replace("last","first")
str1
'my name is alireza, and alireza is my first name'

text = "some of the stuff"
new_text = text.replace("some of", "all")
new_text = new_text.replace("stuff", "things")
new_text
'all the things'