Python BASICS (6) -- conditions and loops

1. output with commas

Print to print the expression-whether it is a string or a string of other types after automatic conversion. It is also feasible to print multiple expressions, as long as they are separated by commas:

>>>  ,4242 >>> 1,2,31, 2, 3>>>  1,2,31 2 3>>> (1,2,31, 2, 3)

A space is inserted between each parameter.

2. import one thing as another

When importing functions from a module, you can use

Import somemodule

Or

From somemodule import somefunction

Or

From somemodule import somefunction, anotherfunction, yetanotherfunction

Or

From somemodule import *

If both modules have open functions, you only need to use the first method to import them, and then use the functions as follows:

Module1.open (...)

Module2.open (...)

Alternatively, you can add an as clause at the end of the statement to give a name after the clause, or provide an alias for the entire module:

>>> >>> foobar.sqrt(42.0>>> >>>  math >>> foobar(42.0

3. Multiple values can be assigned at the same time:

>>> x,y,z=1,2,3>>> 1 2 3>>> >>> x,y=>>> 2 1 3

What we do here is sequential unpacking-Unlocking the sequences of multiple values and placing them in the sequence of variables. A more vivid expression is as follows:

>>> values=1,2,3>>>1, 2, 3>>> x,y,z=>>>1>>>2>>>3

4. chained assignment

Chained assignment is a shortcut to assign the same value to multiple variables.

X = y = somefunction ()

The effect is the same as that of the following statement:

Y = somefunction ()

X = y

5. Incremental assignment

>>> x=2>>> x+=1>>> x*=2>>>6>>> fnord=>>> fnord+=>>> fnord*=2>>>

6. Comparison operators:

Used to compare other objects

In Python, the comparison operation and the assignment operation can be connected. Several operators can be used together, for example, 0 <age <100

7. is: identity Operator

The is operator is used to determine the same identity rather than equality.

>>> x=y=[1,2,3>>> z=[1,2,3>>> x==>>> x==>>> x >>> x 

8. while Loop

>>> x=1>>>  x <=100+=10

9. for Loop

>>> words=[,,,,>>>  word >>> >>> numbers=[0,1,2,3,4,5,6,7,8,9>>>  number  number

>>> range(0,101, 2, 3, 4, 5, 6, 7, 8, 9>>> range(101, 2, 3, 4, 5, 6, 7, 8, 9>>>  number  range(1,101 number

10. cyclically traverse dictionary elements

A simple for statement can loop all the keys of the dictionary, just like the processing sequence:

>>> d={:1,:2,:3>>>  key  key,213

The order of the dictionary elements is usually not defined.

The program can iterate two sequences at the same time:

>>> names=[,,,>>> ages=[12,45,32,102>>>  i  names[i], ,ages[i],

The built-in zip function can also be used for parallel iteration. You can "compress" two sequences and return a list of tuples:

>>> names=[,,,>>> ages=[12,45,32,102>>>, 12), (, 45), (, 32), (, 102>>>  name,age  name,,age,