Python mooc 之玩转数据

Introductions

Key words

Import keyword 

Print(keyword.kwlist)

赋值语句

1） 不需要显示声明，根据值来确定类型

2） 以引用的方式赋值

Pythons 数据类型

布尔型：仅有两个数值，分别是ture 和false 分别使用1，0储存

序列类型：

运算顺序

算术运算 

power > positive or negative value > multiply or divide > exact division> mode > plus or minus 

比较运算

1） 数值比较按大小进行比较

2） 字符串按照ascii 码值大小比较

逻辑运算

-not /and /or. Have the first priorities 

The overall priorities(calculation) of calculation

Module, packages, library 

Module :

Import modulename ( import single module)

Import modulename1, modulename2, ……(import multiple modules)

Or 

From module1 import moduleElement 

Package 

One package consists a large numbers of modules 

Library 

One library consists of lots of packages 

Module 1

条件

If 语句

Sentence:

If expressions: ( expression means the judgement condition )

 Expre_ture_suite ( this means the actions need to carry out when the satisfy the condition)

e.g 

if sd1==sd2

 print(“the square’s are is “, sd1*sd2)

else

if expression:

 expr_true_suite

else:

 expr_ture_suite

e.g 

sd1=int(input(“the first side:”))

sd2=int(input(“the second side:”))

if sd1==sd2:

 print(“ the sqaure’s area is “, sd1*sd2)

else:

 print(“the rectangle’s area is”, sd1*sd2)

elif (multiple condition, multiple assumptions)

sentences :

if expression:

 expr_true_suite

elif expression2:

 expre2_ture_suite 

elif expressionN :

 exprN_ture_suite

else :

 none_of_the_above_s (when the value cannot satisfy any condition above, run this sentence)

e.g 

条件嵌套 （ the sequence of running conditional sentence）

e.g 

range () [function]

Range(start, end, step)

Not indicate the start, it will be automatically stars from 0

Not indicate the step, it will be automatically be 1

NB: the list of numbers do not include the end value, but it include the stared number 

e.g 

range(1,6, 1)

[1,2,3,4,5]

Cycle 

While 

While expression:

 Suite_to_repeat

This cycle also can be understand as not-satisfy-end cycle, which means when the value not longer satisfy expression, this cycle stop.

e.g 

sumA=0

j=1

while j<10:

 sumA+=j

 j+=1 

sumA

 

for 

for iter_var in iterable_object:

 suite_to_repeat

The break, continue and else in the cycle 

Break 

Break terminate the cycle, and turn to run the next sentence 

e.g