格式化输出：str.format()

# 位置参数
print "{} + {} = {}".format(1, 2, 3)
# 1 + 2 = 3

# 指定位置
print "{1} {0}".format("world", "hello")
# hello world

# 关键字参数
print "{name} is {age} years old".format(name="Alice", age=25)
# Alice is 25 years old

# 混合使用
print "{0} + {1} = {result}".format(1, 2, result=3)
# 1 + 2 = 3

class Person(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

p = Person("Alice", 25)
print "{0.name} is {0.age} years old".format(p)
# Alice is 25 years old

data = {"name": "Alice", "age": 25}
print "{0[name]} is {0[age]} years old".format(data)
# Alice is 25 years old

# 用 ** 解包更简洁
print "{name} is {age} years old".format(**data)
# Alice is 25 years old

# 对齐
print "|{:<10}|".format("left")      # |left      |，左对齐
print "|{:>10}|".format("right")     # |     right|，右对齐
print "|{:^10}|".format("center")    # |  center  |，居中

# 填充
print "|{:0>5}|".format(42)           # |00042|，前导零
print "|{:*^10}|".format("hi")       # |***hi****|，* 填充

# 精度
print "{:.2f}".format(3.14159)       # 3.14
print "{:.5}".format("hello world")  # hello，截取 5 个字符

# 千位分隔符
print "{:,}".format(1234567)        # 1,234,567

# 进制
print "{:b}".format(10)              # 1010，二进制
print "{:o}".format(10)              # 12，八进制
print "{:x}".format(255)            # ff，十六进制
print "{:X}".format(255)            # FF，大写十六进制

# 百分比
print "{:.1%}".format(0.25)         # 25.0%

# 宽度 10，精度 2，右对齐
print "|{:10.2f}|".format(3.14159)   # |      3.14|

# 宽度 10，精度 2，左对齐
print "|{:<10.2f}|".format(3.14159) # |3.14      |

# 宽度 10，精度 2，居中
print "|{:^10.2f}|".format(3.14159) # |   3.14   |

data = [
    ("Alice", 25, "Engineer"),
    ("Bob", 30, "Designer"),
    ("Charlie", 35, "Manager"),
]

print "{:<10} {:<5} {:<10}".format("Name", "Age", "Job")
print "-" * 27
for name, age, job in data:
    print "{:<10} {:<5} {:<10}".format(name, age, job)

# 输出：
# Name       Age   Job       
# ---------------------------
# Alice      25    Engineer  
# Bob        30    Designer  
# Charlie    35    Manager   

# 货币
print "${:.2f}".format(1234.5)       # $1234.50

# 科学计数法
print "{:.2e}".format(1234567)      # 1.23e+06

# 带符号
print "{:+d}".format(42)            # +42
print "{: d}".format(42)            #  42（正数前加空格）