字符串格式化 迭代器

1. 百分号方式

常用实例：

tpl = "i am %s" % "alex"

tpl = "i am %s age %d" % ("alex", 18)

tpl = "i am %(name)s age %(age)d" % {"name": "alex", "age": 18}

tpl = "percent %.2f" % 99.97623

tpl = "i am %(pp).2f" % {"pp": 123.425556, }

tpl = "i am %.2f %%" % {"pp": 123.425556, }

2. Format方式

较于百分号方式优点：

可居中，二进制，%

常用实例：

tpl = "i am {}, age {}, {}".format("seven", 18, ‘alex‘)
 
tpl = "i am {}, age {}, {}".format(*["seven", 18, ‘alex‘])
 
tpl = "i am {0}, age {1}, really {0}".format("seven", 18)
 
tpl = "i am {0}, age {1}, really {0}".format(*["seven", 18])
 
tpl = "i am {name}, age {age}, really {name}".format(name="seven", age=18)
 
tpl = "i am {name}, age {age}, really {name}".format(**{"name": "seven", "age": 18})
 
tpl = "i am {0[0]}, age {0[1]}, really {0[2]}".format([1, 2, 3], [11, 22, 33])
 
tpl = "i am {:s}, age {:d}, money {:f}".format("seven", 18, 88888.1)
 
tpl = "i am {:s}, age {:d}".format(*["seven", 18])
 
tpl = "i am {name:s}, age {age:d}".format(name="seven", age=18)
 
tpl = "i am {name:s}, age {age:d}".format(**{"name": "seven", "age": 18})
 
tpl = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2)
 
tpl = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2)
 
tpl = "numbers: {0:b},{0:o},{0:d},{0:x},{0:X}, {0:%}".format(15)
 
tpl = "numbers: {num:b},{num:o},{num:d},{num:x},{num:X}, {num:%}".format(num=15)

3. 迭代器

def myrange(arg):  # 生成器，具有生成能力
    start = 0
    while True:
        if start > arg:
            return
        yield start
        start += 1  # 生成器结束

ret = myrange(10)
for item in ret:  # 封装了迭代器的for循环
    print(item)
# ret.__next__()  # 进入函数找到yield，获取yeild后面的数据
# ret.__next__()

4. 递归

def func(n):
    n += 1
    if n >= 4:
        return "end"
    return func(n)

r = func(1)
print(r)

解释：