python3_03.数据类型
#python字符串格式化:
"this is %d %s bird" % (1, 'dead') # 一般的格式化表达式
"%s---%s---%s" % (42, 3.14, ) # 字符串输出：'42---3.14---'
"%d...%6d...%-6d...%06d" % (1234, 1234, 1234, 1234) # 对齐方式及填充："1234...1234...1234...001234"
x = 1.23456789
"%e | %f | %g" % (x, x, x) # 对齐方式："1.234568e+00 | 1.234568 | 1.23457"
"%6.2f*%-6.2f*%06.2f*%+6.2f" % (x, x, x, x) # 对齐方式：'1.23*1.23*001.23* +1.23'
"%(name1)d---%(name2)s" % {"name1":23, "name2":"value2"} # 基于字典的格式化表达式
"%(name)s is %(age)d" % vars() # vars()函数调用返回一个字典，包含了所有本函数调用时存在的变量
"{0}, {1} and {2}".format('spam', 'ham', 'eggs') # 基于位置的调用
"{motto} and {pork}".format(motto = 'spam', pork = 'ham') # 基于Key的调用
"{motto} and {0}".format(ham, motto = 'spam') # 混合调用
# 添加键 属性 偏移量 (import sys)
"my {1} runs {0.platform}".format(sys, {'spam':'laptop'}) # 基于位置的键和属性
"{config} {sys.platform}".format(sys = sys, config = {'spam':'laptop'}) # 基于Key的键和属性
"first = {0}, second = {0}".format(['A', 'B', 'C']) # 基于位置的偏移量
# 具体格式化
"{0:e}, {1:.3e}, {2:g}".format(3.14159, 3.14159, 3.14159) # 输出'3.141590e+00, 3.142e+00, 3.14159'
"{fieldname:format_spec}".format(......)
# 说明:
"""
fieldname是指定参数的一个数字或关键字, 后边可跟可选的".name"或""成分引用
format_spec ::=[align][#][,][.precision]
fill ::=<any character> #填充字符
align ::="<" | ">" | "=" | "^" #对齐方式
sign ::="+" | "-" | " " #符号说明
width ::=integer #字符串宽度
precision ::=integer #浮点数精度
type ::="b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
"""
# 例子:
'={0:10} = {1:10}'.format('spam', 123.456) # 输出'=spam = 123.456'
'={0:>10}='.format('test') # 输出'= test='
'={0:<10}='.format('test') # 输出'=test ='
'={0:^10}='.format('test') # 输出'= test ='
'{0:X}, {1:o}, {2:b}'.format(255, 255, 255) # 输出'FF, 377, 11111111'
'My name is {0:{1}}.'.format('Fred', 8) # 输出'My name is Fred .'动态指定参数
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