Python输入和输出

格式化输出：

　　print()

　　write()

　　sys.stdout

 

值转化成字符串：

　　repr():

　　　　转化为供解释器读取的形式

　　str():

　　　　转换为供人读取的形式

 

#将字符串输出到一列，并向左侧填充空格以右对齐，同理还有str.ljust,str.center()

str.rjust()

#向数值的字符串表达式填充0

>>> '12'.zfill(5)
'00012'

 

#.format基础用法‘{}’占位

>>> print('We are the {} who say "{}!"'.format('knights', 'Ni'))

We are the knights who say "Ni!"

#关键字参数

print('This {food} is {adjective}.'.format(food='spam', adjective='absolutely horrible'))

#位置参数和关键字参数可以随意组合

print('The story of {0}, {1}, and {other}.'.format('Bill', 'Manfred',other='Georg'))

 

#'!a' (应用 ascii())，'!s' （应用 str() ）和 '!r' （应用 repr() ）可以在格式化之前转换值:

>>> import math

>>> print('The value of PI is approximately {}.'.format(math.pi))

The value of PI is approximately 3.14159265359.

>>> print('The value of PI is approximately {!r}.'.format(math.pi))

The value of PI is approximately 3.141592653589793.

 

# {:} ':' 指令允许对值的格式化加以控制

>>> import math

>>> print('The value of PI is approximately {0:.3f}.'.format(math.pi))

#对较长的字符串用命名引用　　　　

>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678}

>>> print('Jack: {0[Jack]:d}; Sjoerd: {0[Sjoerd]:d}; ''Dcab: {0[Dcab]:d}'.format(table))

 

#%格式化法

>>> import math

>>> print('The value of PI is approximately %5.3f.' % math.pi)

 

 

#>>> print('We are the {} who say "{}!"'.format('knights', 'Ni'))
We are the knights who say "Ni!"