python enumerate 用法，pythonenumerate

python enumerate 用法，pythonenumerate

A new built-in function, enumerate() , will make certain loops a bit clearer. enumerate(thing) , where thing is either an iterator or a sequence, returns a iterator that will return (0, thing [0]) , (1, thing [1]) , (2, thing [2]) , and so forth.

A common idiom to change every element of a list looks like this:

用法：在同時需要index 和 value 值得時候可以使用

line = [1,3,'dfd','jdjfjd']for i in range(len(line)):    item = line[i]    print(i,"--->",item)#運行結果：0 ---> 11 ---> 32 ---> dfd3 ---> jdjfjd

等價於下列代碼：

line = [1,3,'dfd','jdjfjd']for i,item in enumerate(line):    print(i,"-------",item)

 

enumerate 實戰

line 是個 string 包含 0 和 1，要把1都找出來：

#方法一def read_line(line):    sample = {}    n = len(line)    for i in range(n):        if line[i]!='0':            sample[i] = int(line[i])    return sample #方法二def xread_line(line):    return((idx,int(val)) for idx, val in enumerate(line) if val != '0') print read_line('0001110101')print list(xread_line('0001110101'))