引入numpy
import numpy as np
创建numpy数组
countries = np.array([
'Afghanistan', 'Albania', 'Algeria', 'Angola', 'Argentina',
'Armenia', 'Australia', 'Austria', 'Azerbaijan', 'Bahamas',
'Bahrain', 'Bangladesh', 'Barbados', 'Belarus', 'Belgium',
'Belize', 'Benin', 'Bhutan', 'Bolivia',
'Bosnia and Herzegovina'
])
employment = np.array([
55.70000076, 51.40000153, 50.5 , 75.69999695,
58.40000153, 40.09999847, 61.5 , 57.09999847,
60.90000153, 66.59999847, 60.40000153, 68.09999847,
66.90000153, 53.40000153, 48.59999847, 56.79999924,
71.59999847, 58.40000153, 70.40000153, 41.20000076
])
获取数组中某项
print countries[0]
print countries[3]
截取数组中的某一段
print countries[0:3]
print countries[:3]
print countries[17:]
print countries[:]
获取numpy数组的数据类型
print countries.dtype
print employment.dtype
print np.array([0, 1, 2, 3]).dtype
print np.array([1.0, 1.5, 2.0, 2.5]).dtype
print np.array([True, False, True]).dtype
print np.array(['AL', 'AK', 'AZ', 'AR', 'CA']).dtype
循环numpy数组
for country in countries:
print 'Examining country {}'.format(country)
for i in range(len(countries)):
country = countries[i]
country_employment = employment[i]
print 'Country {} has employment {}'.format(country,
country_employment)
numpy的一些内置函数()
print employment.mean() #取平均数
print employment.std() #获取标准差
print employment.max() #取最大值
print employment.sum() #求和
获取最大项的索引值
i = employment.argmax(); #argmax()方法获取employment数组中的最大一项的位置
max_value = employment[i]
max_country = countries[i]
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