Python迭代字典

Question

In [26]: test = {}

In [27]: test["apple"] = "green"

In [28]: test["banana"] = "yellow"

In [29]: test["orange"] = "orange"

In [32]: for fruit, colour in test:
   ....:     print fruit
   ....:     
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/home1/users/joe.borg/<ipython-input-32-8930fa4ae2ac> in <module>()
----> 1 for fruit, colour in test:
      2     print fruit
      3 

ValueError: too many values to unpack

我想要的是迭代測試並獲得密鑰和值。 如果我只是for item in test:我只獲得密鑰。

最終目標的一個例子是：

for fruit, colour in test:
    print "The fruit %s is the colour %s" % (fruit, colour)

Answer 1

在Python 2中你會做：

for fruit, color in test.iteritems():
    # do stuff

在Python 3中，使用items()代替（ iteritems()已被刪除）：

for fruit, color in test.items():
    # do stuff

本教程將介紹這一點。

Answer 2

更改

for fruit, colour in test:
    print "The fruit %s is the colour %s" % (fruit, colour)

至

for fruit, colour in test.items():
    print "The fruit %s is the colour %s" % (fruit, colour)

要么

for fruit, colour in test.iteritems():
    print "The fruit %s is the colour %s" % (fruit, colour)

通常情況下，如果你遍歷一個字典，它只會返回一個鍵，所以這就是它錯誤地說“解壓縮的值太多”的原因。 相反， items或iteritems將返回key value pair list of tuples或iterator以迭代key and values 。

或者，您始終可以通過鍵訪問該值，如以下示例所示

for fruit in test:
    print "The fruit %s is the colour %s" % (fruit, test[fruit])

Answer 3

for key in mydict遍歷鍵。 您想要迭代項目：

for fruit, colour in test.iteritems():
    print "The fruit %s is the colour %s" % (fruit, colour)