Python忽略命令从列表中删除项目

Question

我正在过滤一大堆字典.kept是全局列表,它包含大约9000个字典,所有字典都具有相同的键.我正在尝试删除每个字典,其中'M_P'值大于-4.5,并且有超过一半的字典,所以我创建了一个仅用于其目的的函数.当我检查它们是否已在后来的功能中被删除时,仍然剩下~3000.任何人都可以告诉我为什么会发生这种情况,我相信这些功能会做我告诉它的事吗？

def removeMag():

    countMag = 0
    for mag in kept:
        if to_float(mag['M_P']) > -4.5:
            kept.remove(mag)
            countMag += 1
        else:
            continue

    print '\n'
    print ' Number of mags > -4.5 actually removed: '
    print countMag

def remove_anomalies():    
    count = 0
    count08 = 0
    count09 = 0
    count01 = 0
    countMag = 0
    countMagDim = 0
    #Want to remove Q* < 15 degrees
    for row in kept:
        #to_float(kept(row))
        #Q* greater than 15
        if to_float(row['Q*']) < 15.00:
            kept.remove(row)
        elif to_float(row['vel']) > 80.00:
            kept.remove(row)
        elif to_float(row['err']) >= 0.5*to_float(row['vel']):
            kept.remove(row)

        elif row['log_10_m'] == '?':
            kept.remove(row)
            #print row
            count+=1
        elif row['M_P'] == '?':
            kept.remove(row)
            countMag += 1
        elif to_float(row['M_P']) > -4.5:
            countMagDim += 1

就在这里,我正在检查它.^^^

        elif to_float(row['T_j']) < -50.00 or to_float(row['T_j'] >    50.00):
        kept.remove(row)
        count01 += 1

        #make sure beg height is above end height.
        elif to_float(row['H_beg']) < to_float(row['H_end']):
            kept.remove(row)
        #make sure zenith distance is not greater than 90
        elif to_float(row['eta_p']) > 90.00:
            kept.remove(row)
        #Remove extremities hyperbolic orbits    
        elif (to_float(row['e']) > 2.00 and to_float(row['e']) == 0.00 and to_float(row['a']) == 0.00 and to_float(row['incl']) == 0.00 and to_float(row['omega']) == 0.00 and to_float(row['anode']) == 0.00 and to_float(row['alp_g']) == 0.00 and to_float(row['del_g']) == 0.00 and to_float(row['lam_g']) == 0.00 and to_float(row['bet_g']) == 0.00):
            kept.remove(row)
            count08+=1
        elif to_float(row['q_per']) == 0.00:
            kept.remove(row)
            count09+=1
        elif to_float(row['q_aph']) == 0.00:
            kept.remove(row)
            count09+=1
        else: continue

    print 'Number of dicts with ? as mass value:'
    print count    

    print " Number removed with orbital elements condition: "
    print count08

    print "Number of per or aph equal to 0: "
    print count09

    print "Number of T_j anomalies: "
    print count01

    print "Number of Magnitudes removed from '?': "
    print countMag

以下输出类似于3000.

    print "Number of Magnitudes to be removed from too dim: "
    print countMagDim   
'''    
    print "\n"
    print "log mass values:"
    for row2 in kept:
        print row2['log_10_mass']
    print "\n"
'''

Answer 1

当使用for循环进行迭代时,Python不会自动复制列表,而是直接迭代它.因此,当您删除元素时,循环不会考虑更改,并将跳过列表的元素.

例:

>>> l = [1,2,3,4,5]
>>> for i in l: l.remove(i)
>>> l
[2, 4]

在迭代之前,您可以使用list indice作为速记来制作列表的副本,例如:

>>> for i in l[:]: l.remove(i)
>>> l
[]