Python study notes (2) - if / for / while / String operations
- The if statement
- for statement
- while statement
- String operators
- String in reverse
- String case
- String search
- String encoding
- Analyzing string
- String join / split / count
The if statement
""" if expression: Expression is established else: invalid """ a = 10 b = 20 if a > b: print(a) else: print(b)
for statement
for i in range(0, 10): print(i) else: print("finish")
else: behind the statement to end the loop execution, execution will lead to the end continue
pass: the transition statement (do nothing)
continue: skip this cycle
break: out of the loop (not execute the else statement)
while statement
i = 0 while i < 4: i += 1 print(i) else: print("finish")
String operators
a = "Peter" b = "Peter" print(a == b) # True print(a is b) # True print(a + b) # PeterPeter print(a * 5) # PeterPeterPeterPeterPeter print("e" in a) # True print("e" not in a) # False
String in reverse order
= A " Peter " B = " Peter " Print (A [. 1]) # E Print (A [0:. 3:. 1]) # the Pet Print (A [-1: -4: -1]) # RET [Start : end: interval (negative descending)] Print (A [:: -. 1]) # retep string reverse
String case
message = "i am a good man" print(message.capitalize()) # I am a good man print(message.title()) # I Am A Good Man print(message.upper()) # I AM A GOOD MAN print(message.lower()) # i am a good man
String Find
word = "hello world" print(word.find("l", 0, len(word))) print(word.find("w", 0, len(word))) print(word.rfind("l")) print(word.index("l")) # 找不到不返回异常 print(word.replace("world", "me"))
String encoding
word = "hello world" print(word.encode("utf-8")) word = word.encode("utf-8") print(word.decode("utf -8"))
Analyzing string
file = "boy.jpg" print(file.startswith("boy")) print(file.endswith("jpg"))
String join / split / count
join a string concatenation, the open letter string of splicing, the splicing element is disassembled listing
a = "boy" print("-".join(a)) # b-o-y
split Back to list
b = "b-o-y" print(b.split("-"))
count statistics string of letters
word = "hello world" print(word.count("l")) # 3