把a=[[1,2,3],[4,5],[6,7,8,9],['a','b','c']]中元素逐个输出，五种方式（while while ；while for ；for for；for while;..）

while - while

a=[[1,2,3],[4,5],[6,7,8,9],[‘a’,‘b’,‘c’]]

i=0

while i<len(a):

j=0

while j<len(a[i]):

print(a[i][j],end=(’ '))

j+=1

print()

i+=1

while - for

a=[[1,2,3],[4,5],[6,7,8,9],[‘a’,‘b’,‘c’]]

i=0

while i<len(a):

for j in a[i]:

print(j,end=(’ '))

print()

i+=1

for - for

a=[[1,2,3],[4,5],[6,7,8,9],[‘a’,‘b’,‘c’]]

for i in a:

for j in i:

print(j,end=(’ '))

print()

for - while

a=[[1,2,3],[4,5],[6,7,8,9],[‘a’,‘b’,‘c’]]

for i in a:

j=0

while j<len(i):

print(i[j],end=(’ '))

j+=1

print()

for - - in range

a=[[1,2,3],[4,5],[6,7,8,9],[‘a’,‘b’,‘c’]]

for i in range(0,len(a)):

for j in a[i]:

print(j,end=(’ '))

print()