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规范名字 求积 字符串转换成浮点数

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数据学家琪露诺

#1 Created at ... [Delete] [Delete and Lock User]

1 规范名字

def normalize(name):
    return name[0].upper() + name[1:].lower()
    # return name.capitalize()

L1 = ['adam', 'LISA', 'barT']
L2 = list(map(normalize, L1))
print(L2)

2 求积

from functools import reduce
def prod(L):
    def mult(x, y):
        return x * y
    return reduce(mult, L)

print('3 * 5 * 7 * 9 =', prod([3, 5, 7, 9]))

3 字符串转换成浮点数

from functools import reduce
def str2float(s):
    i = 0;
    dot = 0;
    for i in range(len(s)):
        if s[i] == '.':
            s = s[:i] + s[i + 1:]
            dot = len(s) - i
            break

    def fn(x, y):
        return x * 10 + y

    def char2num(s):
        return {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}[s]

    return reduce(fn, map(char2num, s)) / (10 ** dot)

print('str2float(\'123.456\') =', str2float('123.456'))

JOIEUH

#2 Created at ... [Delete] [Delete and Lock User]

第三题，为什么if那你要break。 不是可以不要吗？只要是假就自动跳出 为什么会报错

数据学家琪露诺

#3 Created at ... [Delete] [Delete and Lock User] 
from functools import reduce
def str2float(s):
    dot = 0
    sign = 1
    if s[0] == '-':  # 如果s有负号
        s = s[1:]  # 记下负号后所有字符，s的长度减1
        sign = -1  # # 负号记为-1
    for i in range(len(s)):
        if s[i] == '.':  # 如果s的第i位是小数点
            s = s[:i] + s[i + 1:]  # 删去小数点字符，s的长度减1
            dot = len(s) - i  # 记录小数点位数，小数点唯一
            break  # 运行一次后就跳出循环，因为s的长度本身发生变化

    def fn(x, y):
        return x * 10 + y

    def char2num(s):
        return {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}[s]

    return reduce(fn, map(char2num, s)) / (10 ** dot) * sign


x1 = '123456789'
x2 = '123456.789'
x3 = '-123.456789'
print('str2float(\'', x1, '\') =', str2float(x1))  # str2float(' 123456789 ') = 123456789.0
print('str2float(\'', x2, '\') =', str2float(x2))  # str2float(' 123456.789 ') = 123456.789
print('str2float(\'', x3, '\') =', str2float(x3))  # str2float(' -123.456789 ') = -123.456789

加上符号判断。lambda方法不太会 我的作业地址，欢迎交流指正 https://github.com/xiajava/learn-python3

巴黎的雨_l

#4 Created at ... [Delete] [Delete and Lock User]

我想知道第二题，name[0]为啥会指向每个名字的第一个字母，按道理说不是L中的第一个名字吗？难道默认为adam就是一个list吗？

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