关于python中find()函数的问题

str.find(sub[, start[, end]])

# 基本用法
text = "Hello, world!"
result = text.find("world")
print(result)  # 输出: 7

# 指定搜索范围
result = text.find("o", 5, 10)
print(result)  # 输出: 7

# 未找到子字符串
result = text.find("python")
print(result)  # 输出: -1

if result == -1:
    print("子字符串未找到")
else:
    print(f"子字符串首次出现在索引 {result}")

text = "Hello, World!"
sub = "world"
result = text.lower().find(sub.lower())
print(result)  # 输出: 7

def find_all_occurrences(text, sub):
    occurrences = []
    start = 0
    while True:
        index = text.find(sub, start)
        if index == -1:
            break
        occurrences.append(index)
        start = index + 1
    return occurrences

text = "abracadabra"
sub = "abra"
print(find_all_occurrences(text, sub))  # 输出: [0, 7]