[开发工具]luliyu-python-day06

切片

# 切片: 对序列(字符串和列表/元组)截取一部分的操作
#[start:end:step]
name = "Python Java C++"
print(name[0])
print(name[-1])
print(name[0:6])
print(name[:6])
print(name[1:])
print(name[-3:])
print(name[:8])
print(name[:])
print(name[::1])
print(name[:6:2])
print(name[::2])
print(name[::-1])
print([i for i in range(10)])
print([i for i in range(10)][::-1])
print([i for i in range(9, -1, -1)])
print("1", name[3::-1]) #3 C++  htyP
print("2", name[3::1]) # 2 hon Java C++
print("3", name[-3::1])
print("4", name[-3::-1])
print("4", name[-3:-1:-1])
print("4", name[-3:-1:1])

# 回文数: 正向读和反向读是一样的    121  898
# 找到 1 ~ 1000所有回文数
ls = []
for num in range(1, 1000):
    if num == int(str(num)[::-1]):
        ls.append(num)
print(ls)

字符串

# 字符串
name = "  Python Java C++  "
print(len(name))
print(type(name))  # <class 'str'>

## 1. 去两端空格操作
print(len(name.strip())) # 字符串一但创建不可以更改
name = name.strip()
print(len(name))
# 2. 分割 默认按照空格进行分割
print(name.split()) # ['Python', 'Java', 'C++']
path = "/Users/ericli/opt/anaconda3/python.app/Contents/MacOS/python /Users/ericli/PycharmProjects/luliyu_python/day06/demo26.py"
print(path.split("/"))
# 3. index / find 返回字符中子串位置
print(name.index("Py"))
print(name.index("+"))
print(name.index("+", 14))
# print(name.index("+", 3, 9))  ValueError: substring not found
print("--"*10)
print(name.find("Py"))
print(name.find("+"))
print(name.find("+", 14))
print(name.find("+", 3, 9)) # 找不到返回-1
## 自己实现find函数
def find(ori, sub, start = None, end = None):
    if start is None:
        start = 0
    if end is None:
        end = len(ori)
    for i in range(start, end):
        if ori[i] == sub:
            return i
    return -1
print(find(name, "+"))
print(find(name, "+", 3, 5))
# 4 join 列表变成字符串
ls = ['Python', 'Java', 'C++']
print(" ".join(ls))
print("".join(ls))
print("/".join(ls))
print("_".join(ls))
# 5 replace 替换
from random import randint
prices = [f"${randint(300, 1000)}" for _ in range(10)]
print(prices)
# 求平均价格
sums = 0
for v in prices:
    v = int(v.replace("$", ""))
    sums += v
print(sums/len(prices))

## 词频统计案例
text = "When you When you When,  you When you face, the world alone, "
text = text.replace(",", "")
print(text)
ts = text.split()
print(ts)
# {"When: 10, }
counts = {}
for word in ts:
    counts[word] = counts.get(word, 0) + 1
print(counts)





# class Student():
#     pass
# s = Student()
# print(type(s))


# 递归函数
# 匿名函数
# 高阶函数