python - Filtering data in pandas -

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i working pandas 0.13.0

i have data frame(a) 2.5 million records

i want exclude hundreds of records applying 2 conditions simoultaneusly: records fulfill 2 conditions @ same time.

i want see how many records exclude when applying both conditions:

len(a)   2523250 b=a[(a.cond1=='120.a') & (a.cond2==2012)] len(b) 6010

but when apply conditions obtain final dataframe:

c=a[(a.cond1!='120.a') & (a.cond2!=2012)] len(c) 2214968

in second case '&' working , 'or' doing wrong?

review de morgan's laws. logical negation of & not switching == !=, must swap & |, because want rows either cond1 != '120.a' or cond2 != 2012, i.e., want exclude row if 1 of != conditions true because makes original & statement false.

@edchum's comment above equivalent to

c=a[(a.cond1!='120.a') | (a.cond2!=2012)]

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