Python--for Loop

For loop

The For loop requires a pre-set number of cycles (n), and then executes the statement that is subordinate to the for (n) times.

The basic structure is

For element in sequence:     statement

For example, we edit a file called fordemo.py.

For a in [3,4.4, ' life ']:    print a

This loop takes one element at a time from the table [3,4.4, ' life '] (recall: The table is a sequence), assigns the element to a, and then executes the action (print) that belongs to the for.

Introduces a new Python function, range (), to help you create a table.

IDX = range (5) Print IDX

You can see that the IDX is [0,1,2,3,4]

The function is to create a new table. The elements of this table are integers, starting with 0, the next element is 1 larger than the previous one, until the upper bound is written in the function (excluding the upper bound itself)

Example

For a in range:    print a**2

While loop

The use of the while IS

While condition:    statement

The while loop executes the statement that is subordinate to it until the condition is False (false)

Example

While I <:    print i    i = i + 1

Interrupt loop

Continue # in an execution of a loop, if you encounter continue, skip this execution and proceed to the next operation

Break # Stops execution of the entire loop

For I in range (10):    
        Continue    Print I

When the loop executes to I = 2, the If condition is set, the continue is triggered, the execution is skipped (no print is executed), and the next execution is continued (i = 3).

For I in range:    if i = = 2: Break    Print I

When the loop executes to I = 2, the If condition is set, the break is triggered, and the entire loop stops.

Summarize

Range ()

For element in sequence:

While condition:

Continue

Break

Python--for Loop