字符串函数_自定义实现函数

# 函数实现

# str.count

str_1 = "assdasdxcx"
sg = "a"
num = 0
for i in str_1:
    if i == sg:
        num += 1
print(num)

# str.replace

str_1 = "assdasadxacaaxa"
old="a" #要替换的
new="$" #替换的
new_str="" #生成新的
num=0 # 替换次数
for i in str_1:
    if i ==old :
        if num < 3:
            new_str += new
            num+=1
        else:new_str += i
    else:new_str += i
print(new_str)

# str.index，只能获取第一个

# 获取obj全部的索引

str_1 = "asdxaza"
obj = "a"
num = 0
lis = []
for var in str_1:
    if var == obj:
        lis.append(num)
    num += 1
print(lis)